Asks this instance to store a AuthToken for server.
This method must persist the token t. If issuedFrom is not null, it must associate
the issuedFrom AuthCode with t in storage, such that t can be found again
by issuedFrom's AuthCode.code, even if t has been refreshed later.
Source
FutureOr storeToken(AuthServer server, AuthToken t, {AuthCode issuedFrom});