TCK: Tests do not validate the PrincipalMapper at all

[jhanders34]

Current no TCK tests are making use of the PrincipalMapper API so there is no coverage of the function. This coverage could be contained by having overriding the Policy of PolicyFactory for one of the test and have it do things using the PrincipalMapper

[arjantijms]

The PrincipalMapper is used here:

authorization/tck/app-custom-policy2/src/main/java/ee/jakarta/tck/authorization/test/TestPolicy.java

Line 72 in d41e205

// Use the PrincipalMapper to retrieve the caller principal

That's a low coverage and we should absolutely add additional tests, but the "not at all" is not correct.

[arjantijms]

Although not a TCK test, an example of a Policy using the PrincipalMapper fully is:

https://github.com/eclipse-ee4j/exousia/blob/main/impl/src/main/java/org/glassfish/exousia/modules/def/DefaultPolicy.java

That one can be used to install in a runtime and run security tests (maybe run the entire Servlet, Authentication and Security TCKS). If the PrincipalMapper is implemented correctly, these all should pass with DefaultPolicy.java installed.