feat: Implement OAuth flow for MCP server integration

- Added MCPOAuthManager to handle OAuth authorization.
- Updated MCPServerSave resource to manage OAuth status and callback.
- Introduced new endpoints for OAuth status and callback handling.
- Enhanced user interface to support OAuth authentication type.
- Implemented polling mechanism for OAuth status in MCPServerModal.
- Updated frontend services and endpoints to accommodate new OAuth features.
- Improved error handling and user feedback for OAuth processes.

frontend/src/api/services/userService.ts

@@ -1,6 +1,6 @@
+import { getSessionToken } from '../../utils/providerUtils';
 import apiClient from '../client';
 import endpoints from '../endpoints';
-import { getSessionToken } from '../../utils/providerUtils';
 
 const userService = {
   getConfig: (): Promise<any> => apiClient.get(endpoints.USER.CONFIG, null),
@@ -112,6 +112,8 @@ const userService = {
     apiClient.post(endpoints.USER.MCP_TEST_CONNECTION, data, token),
   saveMCPServer: (data: any, token: string | null): Promise<any> =>
     apiClient.post(endpoints.USER.MCP_SAVE_SERVER, data, token),
+  getMCPOAuthStatus: (task_id: string, token: string | null): Promise<any> =>
+    apiClient.get(endpoints.USER.MCP_OAUTH_STATUS(task_id), token),
   syncConnector: (
     docId: string,
     provider: string,