Backend/moderation: drop Reference.is_deleted column

Now that UMS owns reference visibility, the legacy is_deleted column
is dead. Migration 0151 drops it after the visibility backfill (and
restores it from the moderation visibility on downgrade).
AdminReference.is_deleted is reserved in the proto since the field
shipped to production.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: aapeliv

app/backend/src/couchers/migrations/versions/0155_backend_moderation_ums_coverage_for_.py

@@ -84,8 +84,25 @@ def upgrade() -> None:
         ["id"],
     )
 
+    # The legacy `is_deleted` flag is now subsumed by UMS visibility (deleted rows were
+    # backfilled to 'hidden' above). Drop the column.
+    op.drop_column("references", "is_deleted")
+
 
 def downgrade() -> None:
+    # Restore the is_deleted column from the moderation visibility before tearing down UMS state.
+    op.add_column(
+        "references",
+        sa.Column("is_deleted", sa.Boolean(), nullable=False, server_default=sa.false()),
+    )
+    op.execute("""
+        UPDATE "references"
+        SET is_deleted = TRUE
+        FROM moderation_states
+        WHERE moderation_states.id = "references".moderation_state_id
+        AND moderation_states.visibility = 'hidden'
+    """)
+
     op.drop_constraint(op.f("fk_references_moderation_state_id_moderation_states"), "references", type_="foreignkey")
     op.drop_index(op.f("ix_references_moderation_state_id"), table_name="references")
     op.drop_column("references", "moderation_state_id")

app/backend/src/couchers/models/rest.py

@@ -431,8 +431,6 @@ class Reference(Base, kw_only=True):
     rating: Mapped[float] = mapped_column(Float)
     was_appropriate: Mapped[bool] = mapped_column(Boolean)
 
-    is_deleted: Mapped[bool] = mapped_column(Boolean, default=False, server_default=expression.false())
-
     from_user: Mapped[User] = relationship(init=False, backref="references_from", foreign_keys="Reference.from_user_id")
     to_user: Mapped[User] = relationship(init=False, backref="references_to", foreign_keys="Reference.to_user_id")
 

app/backend/src/couchers/servicers/admin.py

@@ -185,7 +185,6 @@ def _reference_to_pb(reference: Reference) -> admin_pb2.AdminReference:
         host_request_id=reference.host_request_id or 0,
         rating=reference.rating,
         was_appropriate=reference.was_appropriate,
-        is_deleted=reference.is_deleted,
     )
 
 

app/backend/src/tests/test_admin.py

@@ -737,11 +737,6 @@ def test_DeleteReference_deprecated(db):
             admin_api.DeleteReference(admin_pb2.DeleteReferenceReq(reference_id=reference.reference_id))
         assert e.value.code() == grpc.StatusCode.FAILED_PRECONDITION
 
-    # The reference is unchanged on disk.
-    with session_scope() as session:
-        ref_row = session.execute(select(Reference).where(Reference.id == reference.reference_id)).scalar_one()
-        assert not ref_row.is_deleted
-
 
 def test_GetUserReferences(db):
     super_user, super_token = generate_user(is_superuser=True)
@@ -799,7 +794,6 @@ def test_GetUserReferences(db):
         assert res.references_from[0].from_user_id == user1.id
         assert res.references_from[0].to_user_id == user2.id
         assert res.references_from[0].text == "Reference from user1 to user2"
-        assert res.references_from[0].is_deleted is False
 
         # user1 received 2 references
         assert len(res.references_to) == 2
@@ -810,7 +804,6 @@ def test_GetUserReferences(db):
         assert res.references_to[1].reference_id == ref2.reference_id
         assert res.references_to[1].private_text == "Private note"
         assert res.references_to[1].rating == 0.8
-        assert res.references_to[1].is_deleted is False
 
 
 def test_GetUserReferences_not_found(db):

app/proto/admin.proto

@@ -407,6 +407,9 @@ message GetUserReferencesReq {
 }
 
 message AdminReference {
+  reserved 11;
+  reserved "is_deleted";
+
   int64 reference_id = 1;
   int64 from_user_id = 2;
   int64 to_user_id = 3;
@@ -417,7 +420,6 @@ message AdminReference {
   int64 host_request_id = 8;
   double rating = 9;
   bool was_appropriate = 10;
-  bool is_deleted = 11;
 }
 
 message GetUserReferencesRes {