SetSecurityManager will be removed in a future update

[Bukama]

When I run our build locally with JDK 21 I get the following warnings about the SecurityManager of the @SetEnvironmentVariable (last line highlighted)

WARNING: A terminally deprecated method in java.lang.System has been called
WARNING: System::setSecurityManager has been called by org.junitpioneer.jupiter.EnvironmentVariableUtilsTests$With_SecurityManager (file:/D:/Github/junit-pioneer/build/classes/java/test/)
WARNING: Please consider reporting this to the maintainers of org.junitpioneer.jupiter.EnvironmentVariableUtilsTests$With_SecurityManager
WARNING: System::setSecurityManager will be removed in a future release

Seems we have to rethink our current approach.

[beatngu13]

I like the approach by system stubs mentioned here:

#509 (comment)

This requires Mockito, but we could pull that in the same way as we use Jackson, i.e., as an optional runtime dependency / Gralde feature variant.