as
Returns a TokenProvider backed by this manager's cached token, refreshing it as needed.
Wire this into SpotifyClient or a domain *Apis class to get automatic token refresh on the data path. See getValidAccessToken for refresh behavior per grant and failure semantics.
Return
Token provider that resolves to a valid access token on every call.
Parameters
leeway
Safety window in seconds before actual expiration when the token is treated as expired.