title: OAuth2 server: invalid or missing grant_type parameter
body: <p>I have a NodeJS-based OAuth2 server (using <code>oauth2-server</code> module) started in my LAN. I want to test it with Postman REST Client but I'm getting this error response:</p>
  
  <pre><code>{
      "code": 400,
      "error": "invalid_request",
      "error_description": "Invalid or missing grant_type parameter"
  }
  </code></pre>
  
  <p>This is my request configuration:</p>
  
  <p><img src="https://i.stack.imgur.com/tRXKq.png" alt="Request"></p>
  
  <p>I have tried to send the parameters by URL but I get the error: <code>Method must be POST with application/x-www-form-urlencoded encoding</code>.</p>
  
  <p>Thanks.</p>