TF-1861 Config and abstraction work manager

(cherry picked from commit ee2dca9b34a907c8356ceccf0b23efba2893a01c)

lib/features/offline_mode/observer/sending_email_observer.dart

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+
+import 'package:core/presentation/state/failure.dart';
+import 'package:core/presentation/state/success.dart';
+import 'package:jmap_dart_client/jmap/mail/email/email.dart';
+import 'package:tmail_ui_user/features/offline_mode/observer/work_observer.dart';
+import 'package:tmail_ui_user/features/offline_mode/scheduler/work_status.dart';
+
+class SendingEmailObserver extends WorkObserver<Email> {
+
+  static SendingEmailObserver? _instance;
+
+  SendingEmailObserver._();
+
+  factory SendingEmailObserver() => _instance ??= SendingEmailObserver._();
+
+  @override
+  void handleFailureViewState(Failure failure) {
+  }
+
+  @override
+  void handleSuccessViewState(Success success) {
+  }
+
+  @override
+  WorkStatus observe(Email value) {
+    return WorkStatus.failure;
+  }
+}

lib/features/offline_mode/observer/work_observer.dart

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+
+import 'package:core/presentation/state/failure.dart';
+import 'package:core/presentation/state/success.dart';
+import 'package:core/utils/app_logger.dart';
+import 'package:dartz/dartz.dart';
+import 'package:tmail_ui_user/features/offline_mode/scheduler/work_status.dart';
+
+abstract class WorkObserver<T> {
+  WorkStatus observe(T value);
+
+  void consumeState(Stream<Either<Failure, Success>> newStateStream) {
+    newStateStream.listen(
+      _handleStateStream,
+      onError: (error, stackTrace) {
+        logError('WorkObserver::consumeState():onError:error: $error');
+        logError('WorkObserver::consumeState():onError:stackTrace: $stackTrace');
+      }
+    );
+  }
+
+  void _handleStateStream(Either<Failure, Success> newState) {
+    newState.fold(handleFailureViewState, handleSuccessViewState);
+  }
+
+  void handleFailureViewState(Failure failure);
+
+  void handleSuccessViewState(Success success);
+}