title: Which OAuth2 authentication flow shoud I use for PWA + server side application
body: <p>I am trying to choose the right authentication flow for an application:</p>
  
  <ul>
  <li>Fontend is an Progressive Web App accessible only via HTTPS. It'is done in Angular, Single Page Application.</li>
  <li>External Authorization Server</li>
  <li>Backend accessible via REST calls</li>
  </ul>
  
  <p>For now I am using Authorization Code Grant flow.</p>
  
  <p>What have I tried: </p>
  
  <ul>
  <li>I've checked <a href="https://oauth.net/2/grant-types/" rel="nofollow noreferrer">official site</a>. There is a list of possible flows (Authorization Code, Implicit, Password, Client Credentials, Device Code, ...),
  but no clear indication how to choose between them.</li>
  <li>Then I found <a href="https://auth0.com/docs/api-auth/which-oauth-flow-to-use" rel="nofollow noreferrer">this excellent article</a> on Auth0.com. Unfortunately PWA + server side beckend is not present in their scheme.</li>
  </ul>
  
  <p><strong>Could you please tell me what OAuth2 flow is appropriate to my context and why?</strong></p>