TF-2684 Add button Mail to attendees to open composer with to: all attendees

lib/features/email/domain/model/event_action.dart

@@ -8,7 +8,8 @@ import 'package:tmail_ui_user/main/localizations/app_localizations.dart';
 enum EventActionType {
   yes,
   maybe,
-  no;
+  no,
+  mailToAttendees;
 
   String getLabelButton(BuildContext context) {
     switch(this) {
@@ -18,6 +19,8 @@ enum EventActionType {
         return AppLocalizations.of(context).maybe;
       case EventActionType.no:
         return AppLocalizations.of(context).no;
+      case EventActionType.mailToAttendees:
+        return AppLocalizations.of(context).mailToAttendees;
     }
   }
 
@@ -62,6 +65,10 @@ class EventAction with EquatableMixin {
 
   EventAction(this.actionType, this.link);
 
+  factory EventAction.mailToAttendees() {
+    return EventAction(EventActionType.mailToAttendees, '');
+  }
+
   @override
   List<Object?> get props => [actionType, link];
 }