fix: Add Cascade Delete Function for Transactions and Builds Associated with Flows (#3848)

* refactor: Add cascade delete functionality for flows

This commit adds a new function `cascade_delete_flow` to the `utils.py` file in the `langflow.api` module. This function is responsible for deleting related records when a flow is deleted. It uses the `delete` method from SQLAlchemy to delete records from the `TransactionTable` and `VertexBuildTable` tables based on the flow ID. Finally, it deletes the flow record itself from the `Flow` table.

The function is wrapped in a try-except block to handle any exceptions that may occur during the deletion process. If an exception is raised, a `RuntimeError` is raised with an appropriate error message.

This refactor improves the code by encapsulating the cascade delete logic in a separate function, making it more modular and easier to maintain.

* refactor: Add cascade delete functionality for flows

* refactor: Add cascade delete functionality for flows and folders

* refactor: Remove unused delete_flow_by_id function

* refactor: Add cascade delete functionality for flows and folders

* [autofix.ci] apply automated fixes

---------

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

src/backend/tests/unit/test_database.py

@@ -2,6 +2,7 @@ import json
 from collections import namedtuple
 from uuid import UUID, uuid4
 
+from langflow.services.database.models.folder.model import FolderCreate
 import orjson
 import pytest
 from fastapi.testclient import TestClient
@@ -196,6 +197,75 @@ async def test_delete_flows_with_transaction_and_build(
         assert response.json() == {"vertex_builds": {}}
 
 
+@pytest.mark.asyncio
+async def test_delete_folder_with_flows_with_transaction_and_build(
+    client: TestClient, json_flow: str, active_user, logged_in_headers
+):
+    # Create a new folder
+    folder_name = f"Test Folder {uuid4()}"
+    folder = FolderCreate(name=folder_name, description="Test folder description", components_list=[], flows_list=[])
+
+    response = client.post("/api/v1/folders/", json=folder.model_dump(), headers=logged_in_headers)
+    assert response.status_code == 201, f"Expected status code 201, but got {response.status_code}"
+
+    created_folder = response.json()
+    folder_id = created_folder["id"]
+
+    # Create ten flows
+    number_of_flows = 10
+    flows = [FlowCreate(name=f"Flow {i}", description="description", data={}) for i in range(number_of_flows)]
+    flow_ids = []
+    for flow in flows:
+        flow.folder_id = folder_id
+        response = client.post("api/v1/flows/", json=flow.model_dump(), headers=logged_in_headers)
+        assert response.status_code == 201
+        flow_ids.append(response.json()["id"])
+
+    # Create a transaction for each flow
+    for flow_id in flow_ids:
+        VertexTuple = namedtuple("VertexTuple", ["id"])
+
+        await log_transaction(
+            str(flow_id), source=VertexTuple(id="vid"), target=VertexTuple(id="tid"), status="success"
+        )
+
+    # Create a build for each flow
+    for flow_id in flow_ids:
+        build = {
+            "valid": True,
+            "params": {},
+            "data": ResultDataResponse(),
+            "artifacts": {},
+            "vertex_id": "vid",
+            "flow_id": flow_id,
+        }
+        log_vertex_build(
+            flow_id=build["flow_id"],
+            vertex_id=build["vertex_id"],
+            valid=build["valid"],
+            params=build["params"],
+            data=build["data"],
+            artifacts=build.get("artifacts"),
+        )
+
+    response = client.request("DELETE", f"api/v1/folders/{folder_id}", headers=logged_in_headers)
+    assert response.status_code == 204
+
+    for flow_id in flow_ids:
+        response = client.request(
+            "GET", "api/v1/monitor/transactions", params={"flow_id": flow_id}, headers=logged_in_headers
+        )
+        assert response.status_code == 200
+        assert response.json() == []
+
+    for flow_id in flow_ids:
+        response = client.request(
+            "GET", "api/v1/monitor/builds", params={"flow_id": flow_id}, headers=logged_in_headers
+        )
+        assert response.status_code == 200
+        assert response.json() == {"vertex_builds": {}}
+
+
 def test_create_flows(client: TestClient, session: Session, json_flow: str, logged_in_headers):
     flow = orjson.loads(json_flow)
     data = flow["data"]