fix: refactor database_created hook

src/charm.py

@@ -373,7 +373,7 @@ def _update_workload(self, event: HookEvent) -> None:
     def _on_peer_relation_changed(self, event: RelationChangedEvent) -> None:
         self._update_workload(event)
 
-    @requires_state_setter
+    @requires_state
     def _on_database_created(self, event: DatabaseCreatedEvent) -> None:
         """Database event handler."""
         if not self._container.can_connect():
@@ -386,6 +386,12 @@ def _on_database_created(self, event: DatabaseCreatedEvent) -> None:
             self._update_workload(event)
             return
 
+        if not self.unit.is_leader():
+            logger.info("Unit does not have leadership")
+            self.unit.status = WaitingStatus("Unit waiting for leadership to run the migration")
+            event.defer()
+            return
+
         if not self._run_sql_migration():
             self.unit.status = BlockedStatus("Database migration job failed")
             logger.error("Automigration job failed, please use the schema-upgrade action")