feat(create-source): add create source bloc

- Manages state for source creation form
- Handles input changes for source fields
- Submits new source data to repository
- Loads country data for headquarters selection
- Implements error handling for API calls

Author: fulleni

lib/content_management/bloc/create_source/create_source_bloc.dart

@@ -0,0 +1,141 @@
+import 'package:bloc/bloc.dart';
+import 'package:equatable/equatable.dart';
+import 'package:flutter/foundation.dart';
+import 'package:ht_data_repository/ht_data_repository.dart';
+import 'package:ht_shared/ht_shared.dart';
+
+part 'create_source_event.dart';
+part 'create_source_state.dart';
+
+/// A BLoC to manage the state of creating a new source.
+class CreateSourceBloc extends Bloc<CreateSourceEvent, CreateSourceState> {
+  /// {@macro create_source_bloc}
+  CreateSourceBloc({
+    required HtDataRepository<Source> sourcesRepository,
+    required HtDataRepository<Country> countriesRepository,
+  }) : _sourcesRepository = sourcesRepository,
+       _countriesRepository = countriesRepository,
+       super(const CreateSourceState()) {
+    on<CreateSourceDataLoaded>(_onDataLoaded);
+    on<CreateSourceNameChanged>(_onNameChanged);
+    on<CreateSourceDescriptionChanged>(_onDescriptionChanged);
+    on<CreateSourceUrlChanged>(_onUrlChanged);
+    on<CreateSourceTypeChanged>(_onSourceTypeChanged);
+    on<CreateSourceLanguageChanged>(_onLanguageChanged);
+    on<CreateSourceHeadquartersChanged>(_onHeadquartersChanged);
+    on<CreateSourceSubmitted>(_onSubmitted);
+  }
+
+  final HtDataRepository<Source> _sourcesRepository;
+  final HtDataRepository<Country> _countriesRepository;
+
+  Future<void> _onDataLoaded(
+    CreateSourceDataLoaded event,
+    Emitter<CreateSourceState> emit,
+  ) async {
+    emit(state.copyWith(status: CreateSourceStatus.loading));
+    try {
+      final countriesResponse = await _countriesRepository.readAll();
+      final countries = (countriesResponse as PaginatedResponse<Country>).items;
+
+      emit(
+        state.copyWith(
+          status: CreateSourceStatus.initial,
+          countries: countries,
+        ),
+      );
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: CreateSourceStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: CreateSourceStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+
+  void _onNameChanged(
+    CreateSourceNameChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(name: event.name));
+  }
+
+  void _onDescriptionChanged(
+    CreateSourceDescriptionChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(description: event.description));
+  }
+
+  void _onUrlChanged(
+    CreateSourceUrlChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(url: event.url));
+  }
+
+  void _onSourceTypeChanged(
+    CreateSourceTypeChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(sourceType: () => event.sourceType));
+  }
+
+  void _onLanguageChanged(
+    CreateSourceLanguageChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(language: event.language));
+  }
+
+  void _onHeadquartersChanged(
+    CreateSourceHeadquartersChanged event,
+    Emitter<CreateSourceState> emit,
+  ) {
+    emit(state.copyWith(headquarters: () => event.headquarters));
+  }
+
+  Future<void> _onSubmitted(
+    CreateSourceSubmitted event,
+    Emitter<CreateSourceState> emit,
+  ) async {
+    if (!state.isFormValid) return;
+
+    emit(state.copyWith(status: CreateSourceStatus.submitting));
+    try {
+      final newSource = Source(
+        name: state.name,
+        description: state.description.isNotEmpty ? state.description : null,
+        url: state.url.isNotEmpty ? state.url : null,
+        sourceType: state.sourceType,
+        language: state.language.isNotEmpty ? state.language : null,
+        headquarters: state.headquarters,
+      );
+
+      await _sourcesRepository.create(item: newSource);
+      emit(state.copyWith(status: CreateSourceStatus.success));
+    } on HtHttpException catch (e) {
+      emit(
+        state.copyWith(
+          status: CreateSourceStatus.failure,
+          errorMessage: e.message,
+        ),
+      );
+    } catch (e) {
+      emit(
+        state.copyWith(
+          status: CreateSourceStatus.failure,
+          errorMessage: e.toString(),
+        ),
+      );
+    }
+  }
+}