feat: support refreshtoken (as JWT) from keycloak

[tommytroen]

Fixes #210

• Ensures minimal compatibility with keycloak js client which expects the refresh token to be parseable JWT.
• Creates the refresh token as a Plain JWT (i.e. unsigned) containing nonce and jti if nonce is present in auth request

[tommytroen]

@jp7677 I have created a PR for #210. Went for the semi-hacky solution :) Can you verify on your end that keycloak client works as intended?

[jp7677]

Hi @tommytroen thanks a lot for continuing with my suggestion and turning it into a less hacky solution :)
I just tested your branch here and it works perfectly, so LGTM!

[ybelMekk]

🚢 ?