fix: enforce durable migration ownership and readiness

hub_core/migrations/env.py

@@ -5,6 +5,7 @@ from alembic import context
 from sqlalchemy import engine_from_config, pool
 
 from hub_core.models import Base
+from hub_core.migrations.roles import migration_role_statement
 
 config = context.config
 
@@ -38,6 +39,8 @@ def run_migrations_online() -> None:
         poolclass=pool.NullPool,
     )
     with connectable.connect() as connection:
+        if statement := migration_role_statement(os.environ.get("HUB_CORE_MIGRATION_ROLE")):
+            connection.exec_driver_sql(statement)
         context.configure(connection=connection, target_metadata=target_metadata)
         with context.begin_transaction():
             context.run_migrations()

hub_core/migrations/roles.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+import re
+
+
+def migration_role_statement(role: str | None) -> str | None:
+    """Return a safely quoted SET ROLE statement for an admitted owner role."""
+    if not role:
+        return None
+    if not re.fullmatch(r"[a-z_][a-z0-9_]{0,62}", role):
+        raise ValueError("HUB_CORE_MIGRATION_ROLE is not a safe PostgreSQL role name")
+    return f'SET ROLE "{role}"'