Feature: Support file type messages on widget and dashboard (#659)

- Adds support for file upload

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

app/views/api/v1/widget/messages/index.json.jbuilder

@@ -5,7 +5,7 @@ json.array! @messages do |message|
   json.content_type message.content_type
   json.content_attributes message.content_attributes
   json.created_at message.created_at.to_i
-  json.conversation_id message. conversation_id
+  json.conversation_id message.conversation.display_id
   json.attachment message.attachment.push_event_data if message.attachment
   json.sender message.user.push_event_data if message.user
 end