Seesymfony/symfony#25892

Also, our reference.rst section about the different cache adapters isn't great :).

The cache adapter used by thecache.app service. The FrameworkBundle
ships with multiple adapters:apcu,doctrine,system,filesystem,
psr6,redis andmemcached.

It's not clear what values you wouldactually use, likecache.adapter.redis. It's also not very clear how you would configure, for example, the memcached connection details.