serve workflow templates from custom_nodes (#6193)

* add GET /workflow_templates

* serve workflow templates from custom_nodes

* refactor into custom_node_manager, add test

* remove unused import

* revert changes in folder_paths

* Remove trailing whitespace.

* account for multiple custom_nodes paths

tests-unit/app_test/custom_node_manager_test.py

@@ -0,0 +1,40 @@
+import pytest
+from aiohttp import web
+from unittest.mock import patch
+from app.custom_node_manager import CustomNodeManager
+
+pytestmark = (
+    pytest.mark.asyncio
+)  # This applies the asyncio mark to all test functions in the module
+
+@pytest.fixture
+def custom_node_manager():
+    return CustomNodeManager()
+
+@pytest.fixture
+def app(custom_node_manager):
+    app = web.Application()
+    routes = web.RouteTableDef()
+    custom_node_manager.add_routes(routes, app, [("ComfyUI-TestExtension1", "ComfyUI-TestExtension1")])
+    app.add_routes(routes)
+    return app
+
+async def test_get_workflow_templates(aiohttp_client, app, tmp_path):
+    client = await aiohttp_client(app)
+    # Setup temporary custom nodes file structure with 1 workflow file
+    custom_nodes_dir = tmp_path / "custom_nodes"
+    example_workflows_dir = custom_nodes_dir / "ComfyUI-TestExtension1" / "example_workflows"
+    example_workflows_dir.mkdir(parents=True)
+    template_file = example_workflows_dir / "workflow1.json"
+    template_file.write_text('')
+
+    with patch('folder_paths.folder_names_and_paths', {
+        'custom_nodes': ([str(custom_nodes_dir)], None)
+    }):
+        response = await client.get('/workflow_templates')
+        assert response.status == 200
+        workflows_dict = await response.json()
+        assert isinstance(workflows_dict, dict)
+        assert "ComfyUI-TestExtension1" in workflows_dict
+        assert isinstance(workflows_dict["ComfyUI-TestExtension1"], list)
+        assert workflows_dict["ComfyUI-TestExtension1"][0] == "workflow1"