TF-2667 Show sending message dialog when click send button

model/lib/email/attachment.dart

@@ -68,19 +68,6 @@ enum ContentDisposition {
   other
 }
 
-extension ContentDispositionExtension on ContentDisposition {
-  String get value {
-    switch(this) {
-      case ContentDisposition.inline:
-        return 'inline';
-      case ContentDisposition.attachment:
-        return 'attachment';
-      case ContentDisposition.other:
-        return toString();
-    }
-  }
-}
-
 extension DispositionStringExtension on String? {
   ContentDisposition? toContentDisposition() {
     if (this != null) {

model/lib/extensions/attachment_extension.dart

@@ -1,9 +1,10 @@
 
 import 'package:jmap_dart_client/jmap/mail/email/email_body_part.dart';
-import 'package:model/model.dart';
+import 'package:model/email/attachment.dart';
+import 'package:model/extensions/list_attachment_extension.dart';
 
 extension AttachmentExtension on Attachment {
-  EmailBodyPart toEmailBodyPart({String? disposition, String? charset}) => EmailBodyPart(
+  EmailBodyPart toEmailBodyPart({String? charset}) => EmailBodyPart(
     partId: partId,
     blobId: blobId,
     size: size,
@@ -11,7 +12,7 @@ extension AttachmentExtension on Attachment {
     type: type,
     cid: cid,
     charset: charset,
-    disposition: disposition ?? this.disposition?.value);
+    disposition: disposition?.name ?? ContentDisposition.attachment.name);
 
   Attachment toAttachmentWithDisposition({
     ContentDisposition? disposition,

model/lib/extensions/username_extension.dart

@@ -1,7 +1,8 @@
-
-import 'package:core/presentation/extensions/string_extension.dart';
 import 'package:jmap_dart_client/jmap/core/user_name.dart';
+import 'package:jmap_dart_client/jmap/mail/email/email_address.dart';
 
 extension UsernameExtension on UserName {
-  String get firstCharacter => value.firstLetterToUpperCase.toUpperCase();
+  String get firstCharacter => value.isNotEmpty ? value[0].toUpperCase() : '';
+
+  EmailAddress toEmailAddress() => EmailAddress(null, value);
 }