title: curl send JSON payload
body: <p>I'm just strating with RabbitMQ and I try to send a json payload to it. Unfortunately I'm getting error:</p>
  
  <pre><code>{"error":"bad_request","reason":"payload_not_string"}
  </code></pre>
  
  <p>I read somewhere that I need to use <code>"content_type": "application/json"</code> but that has not helped either.</p>
  
  <p>This is the body I'm trying to send:</p>
  
  <pre><code>{
      "properties": {
          "delivery_mode": 2,
          "content_type": "application/json"
      },
      "routing_key": "git",
      "payload": {
          "action": "created",
          "comment": {
              "url": "https://api.github.com/repos/baxterthehacker/public-repo/comments/11056394",
              "id": 11056394
          }
      },
      "payload_encoding": "string"
  }
  </code></pre>
  
  <p>And the full curl:</p>
  
  <pre><code>curl -i -X POST \
     -H "Content-Type:application/json" \
     -H "Authorization:Basic Z3Vlc3Q6Z3Vlc3Q=" \
     -d \
  '{
      "properties": {
          "delivery_mode": 2,
          "content_type": "application/json"
      },
      "routing_key": "git",
      "payload": {
          "action": "created",
          "comment": {
              "url": "https://api.github.com/repos/baxterthehacker/public-repo/comments/11056394",
              "id": 11056394
          }
      },
      "payload_encoding": "string"
  }' \
   'http://localhost:8090/api/exchanges/%2f/amq.topic/publish'
  </code></pre>
  
  <p>Is it possible to send the json payload at all? I was thinking of sending Github webhooks to one of the queues.</p>