title: Weird error with Facebook Messenger Platform/bot Welcome Confugration
body: <p>I'm getting a weird error while configuring welcome message for my Messenger bot. I've been using the same code (as shown below) and it has just been working fine until last night. I tried it with both cURL and <a href="https://www.getpostman.com/">Postman</a>. Neither of them works.</p>
  
  <pre><code>curl -X POST -H "Content-Type: application/json" -d '{
    "setting_type":"call_to_actions",
    "thread_state":"new_thread",
    "call_to_actions":[
      {
        "message":{
          "text":"Welcome to My Company!"
        }
      }
    ]
  }' "https://graph.facebook.com/v2.6/&lt;PAGE_ID&gt;/thread_settings?access_token=&lt;PAGE_ACCESS_TOKEN&gt;"
  </code></pre>
  
  <p><strong>Error message when executing the code above:</strong></p>
  
  <pre><code>{"error":{"message":"(#100) Invalid keys \"message\" were found in param \"call_to_actions[0]\".","type":"OAuthException","code":100,"fbtrace_id":"Hn42Wa+hapI"}}%
  </code></pre>
  
  <p>I can confirm both PAGE_ID and PAGE_ACCESS_TOKEN are correct as trying to delete the welcome message with the following code works fine. </p>
  
  <pre><code>curl -X POST -H "Content-Type: application/json" -d '{
    "setting_type":"call_to_actions",
    "thread_state":"new_thread",
    "call_to_actions":[
      {
        "message":{
          "text":"Welcome to My Company!"
        }
      }
    ]
  }' "https://graph.facebook.com/v2.6/&lt;PAGE_ID&gt;/thread_settings?access_token=&lt;PAGE_ACCESS_TOKEN&gt;"
  </code></pre>
  
  <p>Also, the code I'm using is exactly the same as shown on the <a href="https://developers.facebook.com/docs/messenger-platform/send-api-reference#welcome_message_configuration">Facebook official API doc</a>. I don't understand why it's saying "message" is not a valid key. Is anyone experiencing the same problem? Did Facebook change their api?</p>
  
  <p>Any help will be much appreciated! </p>