Improve OpenID Connect claims request parameter implementation

_nynymike commented on Oct 17, 2019_
The claims request parameter is specified here:
https://openid.net/specs/openid-connect-core-1_0.html#ClaimsParameter

The admin should be able to see a view of all the claims that are available for a client. Are these claims released via an associated scopes? Or are the explicitly released?

We may want to add claims for:

- Subject attributes
- Client attributes
- Context attributes
- Static Text
- Claims request parameter of signed request object
- client certificate used to perform mutual TLS connection

Perhaps to include the above claims, we can expose a "claims interception script" that can be mapped from the client.

This would also enable us to call out to external claim providers.