Enable mapping multiple ports exposed by single application

[abstractj]

What:

Applications may expose different endpoints on different ports, for example one for main request and another for monitoring/health endpoints. It should be possible to configure Gatekeeper to map different incoming ports to the different ports exposed by the application as currently it would be required to have multiple instance of Gatekeeper executing.

Reference:

• KEYCLOAK-9379 - Enable mapping multiple ports exposed by single application
• [KEYCLOAK-9379] Health, metrics and profiling on separate port #464