[FEATURE] Function param on base token auth handlers

[shurwit]

Is your feature request related to a problem? Please describe.
Currently we need to define a separate base auth handler type to handle any required additional checks.

Describe the solution you'd like
We should allow a function to be passed in to the base tokenauth.Handlers that performs the additional checks required.

Describe alternatives you've considered
We could define a separete handler that performs these additional checks in the implementing service and embed a standard handler, however this will lead to inefficiencies in the order of the checks and require additional overhead of defining a handler for each type.