title: The mandatory 'Content-Type' header is missing
body: <p>I was working on asp.net web api and used OpenIdDict as a way to add authorization. I got some problems, which I quickly resolved, but got stuck on one. Whenever I call the Exchange from the controller, it returns 400 and a response body:</p>
  <pre><code>{
    &quot;error&quot;: &quot;invalid_request&quot;,
    &quot;error_description&quot;: &quot;The mandatory 'Content-Type' header is missing.&quot;,
    &quot;error_uri&quot;: &quot;https://documentation.openiddict.com/errors/ID2081&quot;
  }
  </code></pre>
  <p>I have experimented and searched more and found out, that the 1 part causing the problem is this:</p>
  <pre><code>        [HttpPost(&quot;~/connect/token&quot;)]
          [Produces(&quot;application/json&quot;, &quot;application/vnd.my.v1+json&quot;)]
  </code></pre>
  <p>the post runs as intended, but the 'produces' can't define the content-type for the request and that's why I get an error. Even know all this, I don't know how to resolve the error. I have even re-tested an already working project and the same error occurred.</p>