Feature: log allowed groups based on environment variable

[ValenberghsSven]

For context: we use a service that warms up the cache after a release.
We have many different allowed groups between user profiles.
That service has a list of those allowed groups and will warm up some data for each of those profiles.

For testing if allowed groups are set up correctly it might be handy to have an environment variable that would enable logging of incoming allowed groups when the cache is called.
Similar to how LOG_CACHE_KEYS and LOG_CLEAR_KEYS work.