fix: use string instead of enum

Author: huyenltnguyen

mobile-app/lib/models/learn/challenge_model.dart

@@ -23,21 +23,6 @@ enum ChallengeType {
   exam // 17
 }
 
-enum HelpCategory {
-  htmlCss('HTML-CSS'),
-  javascript('JavaScript'),
-  python('Python'),
-  backend('Backend Development'),
-  csharp('C-Sharp'),
-  english('English'),
-  odin('Odin'),
-  euler('Euler'),
-  rosetta('Rosetta');
-
-  final String value;
-  const HelpCategory(this.value);
-}
-
 class Challenge {
   final String id;
   final String block;
@@ -48,7 +33,7 @@ class Challenge {
   final String superBlock;
   final String? videoId;
   final int challengeType;
-  final HelpCategory helpCategory;
+  final String helpCategory;
 
   final List<ChallengeTest> tests;
   final List<ChallengeFile> files;

mobile-app/lib/ui/views/learn/widgets/dynamic_panel/panels/hint/hint_widget_view.dart

@@ -60,7 +60,7 @@ Future<String> genForumLink(
 }) async {
   Challenge? currChallenge = challenge;
 
-  final HelpCategory helpCategory = challenge.helpCategory;
+  final String helpCategory = challenge.helpCategory;
   final String blockTitle = block.name;
 
   final userDeviceInfo = await getDeviceInfo(context);

mobile-app/test/unit/learn_file_controller_test.dart

@@ -18,7 +18,7 @@ void main() {
       dashedName: 'hello-world',
       superBlock: '2022/responsive-web-design',
       challengeType: 1,
-      helpCategory: HelpCategory.htmlCss,
+      helpCategory: 'HTML-CSS',
       tests: [],
       files: [
         ChallengeFile(