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

server.py

@@ -30,6 +30,7 @@ import node_helpers
 from app.frontend_management import FrontendManager
 from app.user_manager import UserManager
 from app.model_manager import ModelFileManager
+from app.custom_node_manager import CustomNodeManager
 from typing import Optional
 from api_server.routes.internal.internal_routes import InternalRoutes
 
@@ -153,6 +154,7 @@ class PromptServer():
 
         self.user_manager = UserManager()
         self.model_file_manager = ModelFileManager()
+        self.custom_node_manager = CustomNodeManager()
         self.internal_routes = InternalRoutes(self)
         self.supports = ["custom_nodes_from_web"]
         self.prompt_queue = None
@@ -697,6 +699,7 @@ class PromptServer():
     def add_routes(self):
         self.user_manager.add_routes(self.routes)
         self.model_file_manager.add_routes(self.routes)
+        self.custom_node_manager.add_routes(self.routes, self.app, nodes.LOADED_MODULE_DIRS.items())
         self.app.add_subapp('/internal', self.internal_routes.get_app())
 
         # Prefix every route with /api for easier matching for delegation.
@@ -713,6 +716,7 @@ class PromptServer():
         self.app.add_routes(api_routes)
         self.app.add_routes(self.routes)
 
+        # Add routes from web extensions.
         for name, dir in nodes.EXTENSION_WEB_DIRS.items():
             self.app.add_routes([web.static('/extensions/' + name, dir)])