title: How do you set Kafka Rest Proxy Key Schema with JSON values?
body: <p>I'm using Kafka 1.1 and Kafka Rest Proxy 4.1.2. I have been keying records from inside Kafka streams using String keys. I want to use Rest Proxy to insert records to be joined, but the keys are getting escaped quotation marks put around them.</p>
  
  <p>I'm sending a <code>POST</code> request to <code>/topics/{someTopic}</code> with <code>Content-Type: application/vnd.kafka.json.v2+json</code> which causes the issue. </p>
  
  <p>With <code>Content-Type: application/vnd.kafka.avro.v2+json</code> and key_schema type: string, the keys do not have extra quotation marks around them, but I'd rather send json values.</p>
  
  <p>This is what I am sending to the <code>/topics</code> endpoint.</p>
  
  <pre><code>{
      "records": [
          { 
              "key": "abc", 
              "value": {"animal": "dog"} 
          }
      ]
  }
  </code></pre>
  
  <p>When I stream the data in Kafka streams, the key is coming out as <code>\"abc\"</code>, and obviously isn't being joined with records with string keys <code>abc</code>.</p>
  
  <p>Is there a way to specify a key schema with json values, so that my keys don't get escaped quotation marks around them?</p>