TF-185 [BUG] Fix can not display all parts of email which have multiple html part

lib/features/email/data/datasource/html_datasource.dart

@@ -2,5 +2,5 @@
 import 'package:model/model.dart';
 
 abstract class HtmlDataSource {
-  Future<String> transformToHtml(EmailContent emailContent);
+  Future<EmailContent> transformEmailContent(EmailContent emailContent);
 }

lib/features/email/data/datasource_impl/html_datasource_impl.dart

@@ -9,9 +9,9 @@ class HtmlDataSourceImpl extends HtmlDataSource {
   HtmlDataSourceImpl(this._htmlAnalyzer);
 
   @override
-  Future<String> transformToHtml(EmailContent emailContent) {
+  Future<EmailContent> transformEmailContent(EmailContent emailContent) {
     return Future.sync(() async {
-      return await _htmlAnalyzer.transformToHtml(emailContent);
+      return await _htmlAnalyzer.transformEmailContent(emailContent);
     }).catchError((error) {
       throw error;
     });

lib/features/email/data/local/html_analyzer.dart

@@ -5,13 +5,14 @@ import 'package:model/model.dart';
 
 class HtmlAnalyzer {
 
-  Future<String> transformToHtml(EmailContent emailContent) async {
+  Future<EmailContent> transformEmailContent(EmailContent emailContent) async {
     switch(emailContent.type) {
       case EmailContentType.textHtml:
         final htmlTransform = HtmlTransform(emailContent.content);
-        return htmlTransform.transformToHtml();
+        final htmlContent = htmlTransform.transformToHtml();
+        return EmailContent(emailContent.type, htmlContent);
       default:
-        return emailContent.content;
+        return emailContent;
     }
   }
 }

lib/features/email/data/repository/email_repository_impl.dart

@@ -72,7 +72,11 @@ class EmailRepositoryImpl extends EmailRepository {
   }
 
   @override
-  Future<String> transformEmailContentToHtml(EmailContent emailContent) {
-    return _htmlDataSource.transformToHtml(emailContent);
+  Future<List<EmailContent>> transformEmailContent(List<EmailContent> emailContents) async {
+    return await Future.wait(emailContents
+      .map((emailContent) async {
+        return await _htmlDataSource.transformEmailContent(emailContent);
+      })
+      .toList());
   }
 }