Move container_relations to cart service for cross-service ownership

container_relations is a generic parent/child graph used by blog
(menu_nodes), market (marketplaces), and events (calendars). Move it
to cart as shared infrastructure. All services now call cart actions
(attach-child/detach-child) instead of querying the table directly.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

blog/bp/menu_items/services/menu_items.py

@@ -4,7 +4,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, func
 from shared.models.menu_node import MenuNode
 from models.ghost_content import Post
-from shared.services.relationships import attach_child, detach_child
+from shared.infrastructure.actions import call_action
 
 
 class MenuItemError(ValueError):
@@ -80,7 +80,10 @@ async def create_menu_item(
     )
     session.add(menu_node)
     await session.flush()
-    await attach_child(session, "page", post_id, "menu_node", menu_node.id)
+    await call_action("cart", "attach-child", payload={
+        "parent_type": "page", "parent_id": post_id,
+        "child_type": "menu_node", "child_id": menu_node.id,
+    })
 
     return menu_node
 
@@ -131,8 +134,14 @@ async def update_menu_item(
     await session.flush()
 
     if post_id is not None and post_id != old_post_id:
-        await detach_child(session, "page", old_post_id, "menu_node", menu_node.id)
+        await call_action("cart", "detach-child", payload={
-        await attach_child(session, "page", post_id, "menu_node", menu_node.id)
+            "parent_type": "page", "parent_id": old_post_id,
+            "child_type": "menu_node", "child_id": menu_node.id,
+        })
+        await call_action("cart", "attach-child", payload={
+            "parent_type": "page", "parent_id": post_id,
+            "child_type": "menu_node", "child_id": menu_node.id,
+        })
 
     return menu_node
 
@@ -145,7 +154,10 @@ async def delete_menu_item(session: AsyncSession, item_id: int) -> bool:
 
     menu_node.deleted_at = func.now()
     await session.flush()
-    await detach_child(session, "page", menu_node.container_id, "menu_node", menu_node.id)
+    await call_action("cart", "detach-child", payload={
+        "parent_type": "page", "parent_id": menu_node.container_id,
+        "child_type": "menu_node", "child_id": menu_node.id,
+    })
 
     return True
 

cart/alembic/env.py

@@ -5,10 +5,11 @@ MODELS = [
     "shared.models.market",       # CartItem lives here
     "shared.models.order",
     "shared.models.page_config",
+    "shared.models.container_relation",
 ]
 
 TABLES = frozenset({
-    "cart_items", "orders", "order_items", "page_configs",
+    "cart_items", "orders", "order_items", "page_configs", "container_relations",
 })
 
 run_alembic(context.config, MODELS, TABLES)

cart/alembic/versions/0003_add_container_relations.py

@@ -0,0 +1,40 @@
+"""Add container_relations table to cart DB.
+
+Generic parent/child graph for inter-service container relationships
+(page→market, page→calendar, page→menu_node, etc.).
+
+Revision ID: cart_0003
+Revises: cart_0002
+Create Date: 2026-02-26
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "cart_0003"
+down_revision = "cart_0002"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "container_relations",
+        sa.Column("id", sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column("parent_type", sa.String(32), nullable=False),
+        sa.Column("parent_id", sa.Integer, nullable=False),
+        sa.Column("child_type", sa.String(32), nullable=False),
+        sa.Column("child_id", sa.Integer, nullable=False),
+        sa.Column("sort_order", sa.Integer, nullable=False, server_default="0"),
+        sa.Column("label", sa.String(255), nullable=True),
+        sa.Column("created_at", sa.DateTime(timezone=True), server_default=sa.func.now(), nullable=False),
+        sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
+        sa.UniqueConstraint("parent_type", "parent_id", "child_type", "child_id",
+                            name="uq_container_relations_parent_child"),
+    )
+    op.create_index("ix_container_relations_parent", "container_relations", ["parent_type", "parent_id"])
+    op.create_index("ix_container_relations_child", "container_relations", ["child_type", "child_id"])
+
+
+def downgrade() -> None:
+    op.drop_table("container_relations")

cart/bp/actions/routes.py

@@ -109,4 +109,47 @@ def register() -> Blueprint:
 
     _handlers["update-page-config"] = _update_page_config
 
+    # --- attach-child ---
+    async def _attach_child():
+        """Create or revive a ContainerRelation."""
+        from shared.services.relationships import attach_child
+
+        data = await request.get_json(force=True)
+        rel = await attach_child(
+            g.s,
+            parent_type=data["parent_type"],
+            parent_id=data["parent_id"],
+            child_type=data["child_type"],
+            child_id=data["child_id"],
+            label=data.get("label"),
+            sort_order=data.get("sort_order"),
+        )
+        return {
+            "id": rel.id,
+            "parent_type": rel.parent_type,
+            "parent_id": rel.parent_id,
+            "child_type": rel.child_type,
+            "child_id": rel.child_id,
+            "sort_order": rel.sort_order,
+        }
+
+    _handlers["attach-child"] = _attach_child
+
+    # --- detach-child ---
+    async def _detach_child():
+        """Soft-delete a ContainerRelation."""
+        from shared.services.relationships import detach_child
+
+        data = await request.get_json(force=True)
+        deleted = await detach_child(
+            g.s,
+            parent_type=data["parent_type"],
+            parent_id=data["parent_id"],
+            child_type=data["child_type"],
+            child_id=data["child_id"],
+        )
+        return {"deleted": deleted}
+
+    _handlers["detach-child"] = _detach_child
+
     return bp

cart/bp/data/routes.py

@@ -171,6 +171,32 @@ def register() -> Blueprint:
 
     _handlers["page-configs-batch"] = _page_configs_batch
 
+    # --- get-children ---
+    async def _get_children():
+        """Return ContainerRelation children for a parent."""
+        from shared.services.relationships import get_children
+
+        parent_type = request.args.get("parent_type", "")
+        parent_id = request.args.get("parent_id", type=int)
+        child_type = request.args.get("child_type")
+        if not parent_type or parent_id is None:
+            return []
+        rels = await get_children(g.s, parent_type, parent_id, child_type)
+        return [
+            {
+                "id": r.id,
+                "parent_type": r.parent_type,
+                "parent_id": r.parent_id,
+                "child_type": r.child_type,
+                "child_id": r.child_id,
+                "sort_order": r.sort_order,
+                "label": r.label,
+            }
+            for r in rels
+        ]
+
+    _handlers["get-children"] = _get_children
+
     return bp
 
 

events/bp/calendars/services/calendars.py

@@ -6,7 +6,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from models.calendars import Calendar
 from shared.infrastructure.data_client import fetch_data
 from shared.contracts.dtos import PostDTO, dto_from_dict
-from shared.services.relationships import attach_child, detach_child
+from shared.infrastructure.actions import call_action
 import unicodedata
 import re
 
@@ -71,7 +71,10 @@ async def soft_delete(sess: AsyncSession, post_slug: str, calendar_slug: str) ->
 
     cal.deleted_at = utcnow()
     await sess.flush()
-    await detach_child(sess, "page", cal.container_id, "calendar", cal.id)
+    await call_action("cart", "detach-child", payload={
+        "parent_type": "page", "parent_id": cal.container_id,
+        "child_type": "calendar", "child_id": cal.id,
+    })
     return True
 
 async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calendar:
@@ -105,14 +108,20 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
         if existing.deleted_at is not None:
             existing.deleted_at = None  # revive
             await sess.flush()
-            await attach_child(sess, "page", post_id, "calendar", existing.id)
+            await call_action("cart", "attach-child", payload={
+                "parent_type": "page", "parent_id": post_id,
+                "child_type": "calendar", "child_id": existing.id,
+            })
             return existing
         raise CalendarError(f'Calendar with slug "{slug}" already exists for post {post_id}.')
 
     cal = Calendar(container_type="page", container_id=post_id, name=name, slug=slug)
     sess.add(cal)
     await sess.flush()
-    await attach_child(sess, "page", post_id, "calendar", cal.id)
+    await call_action("cart", "attach-child", payload={
+        "parent_type": "page", "parent_id": post_id,
+        "child_type": "calendar", "child_id": cal.id,
+    })
     return cal
 
 

shared/services/market_impl.py

@@ -12,7 +12,7 @@ from shared.models.market import Product
 from shared.models.market_place import MarketPlace
 from shared.browser.app.utils import utcnow
 from shared.contracts.dtos import MarketPlaceDTO, ProductDTO
-from shared.services.relationships import attach_child, detach_child
+from shared.infrastructure.actions import call_action
 
 
 def _mp_to_dto(mp: MarketPlace) -> MarketPlaceDTO:
@@ -93,7 +93,10 @@ class SqlMarketService:
                 existing.deleted_at = None  # revive
                 existing.name = name
                 await session.flush()
-                await attach_child(session, container_type, container_id, "market", existing.id)
+                await call_action("cart", "attach-child", payload={
+                    "parent_type": container_type, "parent_id": container_id,
+                    "child_type": "market", "child_id": existing.id,
+                })
                 return _mp_to_dto(existing)
             raise ValueError(f'Market with slug "{slug}" already exists for this container.')
 
@@ -103,7 +106,10 @@ class SqlMarketService:
         )
         session.add(market)
         await session.flush()
-        await attach_child(session, container_type, container_id, "market", market.id)
+        await call_action("cart", "attach-child", payload={
+            "parent_type": container_type, "parent_id": container_id,
+            "child_type": "market", "child_id": market.id,
+        })
         return _mp_to_dto(market)
 
     async def soft_delete_marketplace(
@@ -124,5 +130,8 @@ class SqlMarketService:
 
         market.deleted_at = utcnow()
         await session.flush()
-        await detach_child(session, container_type, container_id, "market", market.id)
+        await call_action("cart", "detach-child", payload={
+            "parent_type": container_type, "parent_id": container_id,
+            "child_type": "market", "child_id": market.id,
+        })
         return True