feat(web,server): link/unlink oauth account (#1154)

* feat(web,server): link/unlink oauth account

* chore: linting

* fix: broken oauth callback

* fix: user core bugs

* fix: tests

* fix: use user response

* chore: update docs

* feat: prevent the same oauth account from being linked twice

* chore: mock logger

mobile/openapi/test/o_auth_api_test.dart

@@ -27,5 +27,15 @@ void main() {
       // TODO
     });
 
+    //Future<UserResponseDto> link(OAuthCallbackDto oAuthCallbackDto) async
+    test('test link', () async {
+      // TODO
+    });
+
+    //Future<UserResponseDto> unlink() async
+    test('test unlink', () async {
+      // TODO
+    });
+
   });
 }