Fix: File upload from slack (#4494)

When you upload a file from slack chat it's not appearing in the chatwoot inbox.
This is because Slack updated the webhook event format

spec/support/slack_stubs.rb

@@ -22,17 +22,7 @@ module SlackStubs
   end
 
   def slack_attachment_stub
-    {
-      token: '[FILTERED]',
-      team_id: 'TLST3048H',
-      api_app_id: 'A012S5UETV4',
-      event: message_event,
-      type: 'event_callback',
-      event_id: 'Ev013QUX3WV6',
-      event_time: 1_588_623_033,
-      authed_users: '[FILTERED]',
-      webhook: {}
-    }
+    slack_message_stub.merge({ event: message_event_without_blocks })
   end
 
   def slack_message_stub_without_thread_ts
@@ -95,15 +85,26 @@ module SlackStubs
         elements: [
           {
             type: 'rich_text_section',
-            elements: [
-              {
-                type: 'text',
-                text: 'this is test'
-              }
-            ]
+            elements: [{
+              type: 'text',
+              text: 'this is test'
+            }]
           }
         ]
       }
     ]
   end
+
+  def message_event_without_blocks
+    {
+      client_msg_id: 'ffc6e64e-6f0c-4a3d-b594-faa6b44e48ab',
+      type: 'message',
+      text: 'this is test <https://chatwoot.com> Hey <@U019KT237LP|Sojan> Test again',
+      user: 'ULYPAKE5S',
+      ts: '1588623033.006000',
+      files: file_stub,
+      thread_ts: '1588623023.005900',
+      channel: 'G01354F6A6Q'
+    }
+  end
 end