WIP: Set audience with UMATokenSourceOption upon UMATokenSource instantiation

[AndrasHacks]

In order to enable the UMATokenSource backed HTTPClient development I needed to have a way to create an UMA Token Source, which supports defining audiences, not only at Token Request time, but at Token Source instantiation time as well. This PR enables that.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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0.0% Duplication

[tadam313]

Let's catch up on this in January, out initial plan was to support audiences via scope mapping which simplifies many things for the clients and also lets us to have well defined scopes to map out other rules for clients based on that. I'd like UMA and OAuth flow to work the same way to avoid confusions at our and the client sides. It's also possible to use scopes with UMA so we can have a standard interface.

Reason behind this:

• scope: "What I want to do?" -> and we map out the possible audiences for the clients
• direct audience setting: "Who I want to talk to?" -> need to have different source for every service that I want to talk to -> quite complex on the client side and we don't have any visibility over this in keycloak.