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/utils/validators.py

@@ -515,7 +515,13 @@ def validate_connector_config(
         },
         "SLACK_CONNECTOR": {"required": ["SLACK_BOT_TOKEN"], "validators": {}},
         "NOTION_CONNECTOR": {
-            "required": ["NOTION_INTEGRATION_TOKEN"],
+            "required": ["access_token"],  # OAuth-based only
+            "optional": [
+                "workspace_id",  # OAuth fields
+                "workspace_name",
+                "workspace_icon",
+                "bot_id",
+            ],
             "validators": {},
         },
         "GITHUB_CONNECTOR": {