feat: add Notion OAuth integration and connector routes

- Introduced Notion OAuth support with new environment variables for client ID, client secret, and redirect URI.
- Implemented Notion connector routes for OAuth flow, including authorization and callback handling.
- Updated existing components to accommodate Notion integration, including validation changes and connector configuration.
- Enhanced the Notion indexer to utilize OAuth access tokens instead of integration tokens.
- Adjusted UI components to reflect the new Notion connector without requiring special configuration.

surfsense_backend/app/routes/__init__.py

@@ -18,6 +18,7 @@ from .google_gmail_add_connector_route import (
 from .logs_routes import router as logs_router
 from .luma_add_connector_route import router as luma_add_connector_router
 from .new_chat_routes import router as new_chat_router
+from .notion_add_connector_route import router as notion_add_connector_router
 from .new_llm_config_routes import router as new_llm_config_router
 from .notes_routes import router as notes_router
 from .podcasts_routes import router as podcasts_router
@@ -40,6 +41,7 @@ router.include_router(google_gmail_add_connector_router)
 router.include_router(google_drive_add_connector_router)
 router.include_router(airtable_add_connector_router)
 router.include_router(luma_add_connector_router)
+router.include_router(notion_add_connector_router)
 router.include_router(new_llm_config_router)  # LLM configs with prompt configuration
 router.include_router(logs_router)
 router.include_router(circleback_webhook_router)  # Circleback meeting webhooks