Add 'keycloak-authorization' integration test based on Wiremock

[sberyozkin]

Description

Testing various keycloak-authorization configuration options, including the caching of the responses, would help to increase the coverage and also show the users how they can quickly test it without having to set up Keycloak

@cemnura Hi - this is another issue we can look at as part of improving the test support for OIDC/Keycloak :-)

[cemnura]

@sberyozkin would love to take a look 👍