feat(content): integrate language picker into create source page

Author: fulleni

lib/content_management/view/create_source_page.dart

@@ -7,6 +7,7 @@ import 'package:flutter_news_app_web_dashboard_full_source_code/content_manageme
 import 'package:flutter_news_app_web_dashboard_full_source_code/content_management/bloc/create_source/create_source_bloc.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/content_management/bloc/edit_source/edit_source_bloc.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/shared/shared.dart';
 import 'package:go_router/go_router.dart';
 import 'package:ui_kit/ui_kit.dart';
@@ -160,15 +161,13 @@ class _CreateSourceViewState extends State<_CreateSourceView> {
                           .add(CreateSourceUrlChanged(value)),
                     ),
                     const SizedBox(height: AppSpacing.lg),
-                    TextFormField(
+                    LanguagePickerFormField(
+                      labelText: l10n.language,
                       initialValue: state.language,
-                      decoration: InputDecoration(
-                        labelText: l10n.language,
-                        border: const OutlineInputBorder(),
-                      ),
-                      onChanged: (value) => context
-                          .read<CreateSourceBloc>()
-                          .add(CreateSourceLanguageChanged(value)),
+                      onChanged: (language) =>
+                          context.read<CreateSourceBloc>().add(
+                                CreateSourceLanguageChanged(language),
+                              ),
                     ),
                     const SizedBox(height: AppSpacing.lg),
                     DropdownButtonFormField<SourceType?>(

lib/shared/widgets/language_picker_form_field.dart

@@ -14,13 +14,15 @@ class LanguagePickerFormField extends FormField<language_picker.Language> {
   /// standard [FormField] properties.
   ///
   /// The [labelText] is displayed as the input field's label.
+  /// The [onChanged] callback is invoked when a new language is selected.
   LanguagePickerFormField({
     super.key,
     super.onSaved,
     super.validator,
     super.initialValue,
     super.autovalidateMode,
     String? labelText,
+    void Function(language_picker.Language)? onChanged,
   }) : super(
           builder: (FormFieldState<language_picker.Language> state) {
             // This controller is just for displaying the text. The actual
@@ -46,6 +48,9 @@ class LanguagePickerFormField extends FormField<language_picker.Language> {
                       state.value ?? language_picker.Languages.english,
                   onValuePicked: (language_picker.Language language) {
                     state.didChange(language);
+                    if (onChanged != null) {
+                      onChanged(language);
+                    }
                     // Update the text in the read-only text field.
                     controller.text = language.name;
                   },