Add debug mode with more info #654

Currently there is no easy way to investigate transient errors. Usually they happen under certain conditions, so we need an ability to trace the state of the library to be able to reproduce those conditions.

Couple suggestions:

1. Add a debugging mode with verbose logging on all the components of a library.
2. Always trace issuer claim when there is an error refreshing the token - this will help to investigate rare production issues when debugging mode is not an option.