Powermock does not support JUnit5 yet, so we need to remove it
to support JUnit 5. Additionally, maintaining additional libraries
adds extra work for the team.
Mockito now supports final classes and static method mocking. This
commit replaces Powermock with mockito-inline.
Closes gh-6025
Adding JwtDecoders#fromOidcIssuerLocation which takes an issuer
and derives from it the jwk set uri via a call to
.well-known/openid-configuration
Fixes: gh-5523