feat(api): Introduce workflow pause state management (#27298)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/app/layers/pause_state_persist_layer.py

@@ -0,0 +1,71 @@
+from sqlalchemy import Engine
+from sqlalchemy.orm import sessionmaker
+
+from core.workflow.graph_engine.layers.base import GraphEngineLayer
+from core.workflow.graph_events.base import GraphEngineEvent
+from core.workflow.graph_events.graph import GraphRunPausedEvent
+from repositories.api_workflow_run_repository import APIWorkflowRunRepository
+from repositories.factory import DifyAPIRepositoryFactory
+
+
+class PauseStatePersistenceLayer(GraphEngineLayer):
+    def __init__(self, session_factory: Engine | sessionmaker, state_owner_user_id: str):
+        """Create a PauseStatePersistenceLayer.
+
+        The `state_owner_user_id` is used when creating state file for pause.
+        It generally should id of the creator of workflow.
+        """
+        if isinstance(session_factory, Engine):
+            session_factory = sessionmaker(session_factory)
+        self._session_maker = session_factory
+        self._state_owner_user_id = state_owner_user_id
+
+    def _get_repo(self) -> APIWorkflowRunRepository:
+        return DifyAPIRepositoryFactory.create_api_workflow_run_repository(self._session_maker)
+
+    def on_graph_start(self) -> None:
+        """
+        Called when graph execution starts.
+
+        This is called after the engine has been initialized but before any nodes
+        are executed. Layers can use this to set up resources or log start information.
+        """
+        pass
+
+    def on_event(self, event: GraphEngineEvent) -> None:
+        """
+        Called for every event emitted by the engine.
+
+        This method receives all events generated during graph execution, including:
+        - Graph lifecycle events (start, success, failure)
+        - Node execution events (start, success, failure, retry)
+        - Stream events for response nodes
+        - Container events (iteration, loop)
+
+        Args:
+            event: The event emitted by the engine
+        """
+        if not isinstance(event, GraphRunPausedEvent):
+            return
+
+        assert self.graph_runtime_state is not None
+        workflow_run_id: str | None = self.graph_runtime_state.system_variable.workflow_execution_id
+        assert workflow_run_id is not None
+        repo = self._get_repo()
+        repo.create_workflow_pause(
+            workflow_run_id=workflow_run_id,
+            state_owner_user_id=self._state_owner_user_id,
+            state=self.graph_runtime_state.dumps(),
+        )
+
+    def on_graph_end(self, error: Exception | None) -> None:
+        """
+        Called when graph execution ends.
+
+        This is called after all nodes have been executed or when execution is
+        aborted. Layers can use this to clean up resources or log final state.
+
+        Args:
+            error: The exception that caused execution to fail, or None if successful
+        """
+        pass