Chore: Message to support multiple attachments (#730)

* Changes for the message to have multiple attachments
* changed the message association to attachments from has_one to has_many
* changed all the references of this association in building and fetching to reflect this change

* Added number of attachments validation to the message model

* Modified the backend responses and endpoints to reflect multiple attachment support (#737)

* Changing the frontend components for multiple attachments
* changed the request structure to reflect the multiple attachment structures
* changed the message bubbles to support multiple attachments
* bugfix: agent side attachment was not showing because of a missing await
* broken message was shown because of the store filtering
* Added documentation for ImageMagick

* spec fixes

* refactored code to reflect more apt namings

* Added updated message listener for the dashboard (#727)
* Added the publishing for message updated event
* Implemented the listener for dashboard

Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/services/facebook/send_reply_service.rb

@@ -46,7 +46,7 @@ class Facebook::SendReplyService
         attachment: {
           type: 'image',
           payload: {
-            url: message.attachment.file_url
+            url: message.attachments.first.file_url
           }
         }
       }
@@ -54,7 +54,7 @@ class Facebook::SendReplyService
   end
 
   def fb_message_params
-    if message.attachment.blank?
+    if message.attachments.blank?
       fb_text_message_params
     else
       fb_attachment_message_params