Fetches an access token for the currently logged-in user.
Options for fetching the access token, including optional audience and scope.
The access token as a string.
Passing audience or scope relies on MRRT to be configured in your Auth0 Application.
https://auth0.com/docs/secure/tokens/refresh-tokens/multi-resource-refresh-token/configure-and-implement-multi-resource-refresh-token
Fetches an access token for the currently logged-in user.