How does authorization work with an API and an SPA

That worked!

On the front end I changed my auth0.webAuth to

  auth0 = new auth0.WebAuth({
    clientID: env.authClientId,
    domain: env.authDomain,
    responseType: 'token id_token',
    redirectUri: env.authCallbackUrl,
    scope: 'openid',
    audience: env.authAudience
  });

Then in the Http headers to the backend i use:

'Authorization': `Bearer ${this.accessToken}`