TF-725 Implement UI/UX for insert image to composer on web

model/lib/extensions/attachment_extension.dart

@@ -3,10 +3,28 @@ import 'package:jmap_dart_client/jmap/mail/email/email_body_part.dart';
 import 'package:model/model.dart';
 
 extension AttachmentExtension on Attachment {
-  EmailBodyPart toEmailBodyPart(String disposition) => EmailBodyPart(
+  EmailBodyPart toEmailBodyPart({String? disposition, String? charset}) => EmailBodyPart(
+    partId: partId,
     blobId: blobId,
     size: size,
     name: name,
     type: type,
-    disposition: disposition);
+    cid: cid,
+    charset: charset,
+    disposition: disposition ?? this.disposition?.value);
+
+  Attachment toAttachmentWithDisposition({
+    ContentDisposition? disposition,
+    String? cid
+  }) {
+    return Attachment(
+        partId: partId,
+        blobId: blobId,
+        size: size,
+        name: name,
+        type: type,
+        cid: cid ?? this.cid,
+        disposition: disposition ?? this.disposition
+    );
+  }
 }

model/lib/upload/file_info.dart

@@ -15,6 +15,8 @@ class FileInfo with EquatableMixin {
     return FileInfo('', '', 0);
   }
 
+  String get fileExtension => fileName.split('.').last;
+
   String get mimeType => lookupMimeType(kIsWeb ? fileName : filePath) ?? 'application/json; charset=UTF-8';
 
   @override