fix: Save content_type, multipart information to email message model (#2774)

app/presenters/mail_presenter.rb

@@ -61,17 +61,19 @@ class MailPresenter < SimpleDelegator
 
   def serialized_data
     {
-      text_content: text_content,
+      bcc: bcc,
+      cc: cc,
+      content_type: content_type,
+      date: date,
+      from: from,
       html_content: html_content,
+      in_reply_to: in_reply_to,
+      message_id: message_id,
+      multipart: multipart?,
       number_of_attachments: number_of_attachments,
       subject: subject,
-      date: date,
-      to: to,
-      from: from,
-      in_reply_to: in_reply_to,
-      cc: cc,
-      bcc: bcc,
-      message_id: message_id
+      text_content: text_content,
+      to: to
     }
   end