GET {Authorization Endpoint}?
  response_type=code&
  client_id={Client ID}&
  redirect_uri={Redirect URI}&
  scope={Scopes}&
  state={Arbitrary String}&
  code_challenge=guAPs_oSgp461e5Hp2i9papYt_Z89TyFEphH-UPfBOE& // Wymagane
  code_challenge_method=S256 // Wymagane (lub 'plain' - niezalecane)
HTTP/1.1
Host: {Authorization Server}
