Allow admin-cli to authenticate with credentials

[Fristi]

Hi!

Thanks for this great library, I was writing a client myself but this one is way more complete. I would be interested in contributing if there is overlap in our needs :-)

In my previous client I used credentials to authenticate with the master admin-cli client. The reason for that is because the importing of a realm-export can only be done to a new realm. So if you want to override settings for the master realm, you cannot do this automated (I couldn't find it atleast).

I think making KeycloakConfig.Auth an ADT which has two members Secret and Credentials which will be used in the TokenManager to exchange a token the way to go? What do you think?

Greets,

Mark

[lmuller90]

Hey Mark!

Appreciate the feedback, admittedly the methods we have of authenticating with the master admin-cli client is rather restrictive at the moment. Looking into expanding it with your suggestion in mind, will tag you into the PR when it's up so you can confirm if our solution suits your needs.

Regards,
Louis