This is the Access Token Response, a simple value-object that holds the result of the
from an Access Token Request, as listed in RFC 6749:
4.1.4 - Authorization Code grant - Access Token Response,
4.2.2 - Implicit Grant - Access Token Response,
4.3.3 - Resource Owner Password Credentials Grant - Access Token Response
4.4.3 - Client Credentials Grant - Access Token Response