feat(db): add idempotent Alembic migration for GOOGLE_DRIVE_CONNECTOR enums

surfsense_backend/alembic/versions/54_add_google_drive_connector_enums.py

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+"""Add Google Drive connector enums
+
+Revision ID: 54
+Revises: 53
+Create Date: 2025-12-28 12:00:00.000000
+
+"""
+
+from collections.abc import Sequence
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "54"
+down_revision: str | None = "53"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Safely add 'GOOGLE_DRIVE_CONNECTOR' to enum types if missing."""
+
+    # Add to searchsourceconnectortype enum
+    op.execute(
+        """
+    DO $$
+    BEGIN
+        IF NOT EXISTS (
+            SELECT 1 FROM pg_type t
+            JOIN pg_enum e ON t.oid = e.enumtypid
+            WHERE t.typname = 'searchsourceconnectortype' AND e.enumlabel = 'GOOGLE_DRIVE_CONNECTOR'
+        ) THEN
+            ALTER TYPE searchsourceconnectortype ADD VALUE 'GOOGLE_DRIVE_CONNECTOR';
+        END IF;
+    END
+    $$;
+    """
+    )
+
+    # Add to documenttype enum
+    op.execute(
+        """
+    DO $$
+    BEGIN
+        IF NOT EXISTS (
+            SELECT 1 FROM pg_type t
+            JOIN pg_enum e ON t.oid = e.enumtypid
+            WHERE t.typname = 'documenttype' AND e.enumlabel = 'GOOGLE_DRIVE_CONNECTOR'
+        ) THEN
+            ALTER TYPE documenttype ADD VALUE 'GOOGLE_DRIVE_CONNECTOR';
+        END IF;
+    END
+    $$;
+    """
+    )
+
+
+def downgrade() -> None:
+    """Remove 'GOOGLE_DRIVE_CONNECTOR' from enum types.
+    
+    Note: PostgreSQL doesn't support removing enum values directly.
+    This would require recreating the enum type, which is complex and risky.
+    For now, we'll leave the enum values in place.
+    
+    In a production environment with strict downgrade requirements, you would need to:
+    1. Create new enum types without the value
+    2. Convert all columns to use the new type
+    3. Drop the old enum type
+    4. Rename the new type to the old name
+    
+    This is left as pass to avoid accidental data loss.
+    """
+    pass
+