title: How to get an access token from Google without an api library?
body: <p>I am working on an Elixir Phoenix web project where I want to interact with Google's Indexing API.</p>
  
  <p>Google uses OAuth2 to authenticate api requests and actually has a decent <a href="https://developers.google.com/search/apis/indexing-api/v3/prereqs" rel="nofollow noreferrer">documentation</a> on this.</p>
  
  <p>But it only explains the process using one of the supported libraries in Python, Java, PHP or JS.</p>
  
  <p>I would like to make the HTTP requests by myself to retrieve that access token. But the request format (including headers or parameters) is nowhere documented and I cannot even figure out from the libraries' source code.</p>
  
  <p>I have tried requesting <a href="https://accounts.google.com/o/oauth2/token" rel="nofollow noreferrer">https://accounts.google.com/o/oauth2/token</a> (also other eligible URLs) in Postman with the "OAuth 2.0" request type.
  But it was all just guessing and trying. All the research did not help.</p>