fix(server): don't publicly reveal user count (#4409)

* fix: don't reveal user count publicly

* fix: mobile and user controller

* fix: update other frontend endpoints

* fix: revert openapi change

* chore: open api

* fix: initialize

* openapi

---------

Co-authored-by: Alex Tran <alex.tran1502@gmail.com>

mobile/openapi/test/server_config_dto_test.dart

@@ -16,6 +16,11 @@ void main() {
   // final instance = ServerConfigDto();
 
   group('test ServerConfigDto', () {
+    // bool isInitialized
+    test('to test the property `isInitialized`', () async {
+      // TODO
+    });
+
     // String loginPageMessage
     test('to test the property `loginPageMessage`', () async {
       // TODO