Add support for composite name claims

[vlaurin]

By default, QuickCase expect the full name to be extracted from a single, overridable name claim. However, this doesn't offer support for configurations where the name claim is not used and instead claims given_name and family_name are used in conjunction.

Support should be added to allow name to be configured as the concatenation of multiple claims, for example using a template string.

quickcase:
  oidc:
    claims:
      names: '${given_name} ${family_name}'