title: POST REFUND returned error 400 since Feb ~10th
body: <p>I have a script processing some refund payments that does not work anymore since approx. Feb 10th. Server responds Content-Type is not supported ... even if my header Content-Type looks actually correct</p>
  
  <p>Same code worked before that date which makes me believe something was changed on the server side but I haven't notice anything in the square-connect API changelog recently that would explain this problem. </p>
  
  <p>Any help would be much appreciated :)
  Thanks</p>
  
  <p>See below JSON request and response.</p>
  
  <pre><code>{"method":"POST",
    "headers":
      {"Authorization":"Bearer [mypersonalid]",
       "Accept":"application/json",
       "Content-Type":"application/json"},
       "payload":
         {"payment_id":"[paymentid]",
          "type":"FULL",
          "reason":"reason"
         }
      }"
  }
  
  
  {"type":"bad_request",
   "message":"The Content-Type of this request is not supported. 
              Supported     type(s): application/json"
  }
  </code></pre>