Add a cta-admin option to invalidate cta-frontend caches

As mentioned in https://gitlab.cern.ch/cta/operations/-/issues/1103#note_6873220, we have no way to invalidate the caches in the cta-frontend (besides restarting the daemons). This causes some issues when changing some configurations (such changing an archive route).

One easy solution is to invalidate the cache when the frontend detects a configuration being added. Unfortunately, if we have multiple frontends, this is will not be propagated between them.

A simple solution - purpose of this issue - is to add a new command to cta-admin:

cta-admin cache invalidate

This command will clear all the caches on the frontend. It can be manually trigged by operations whenever a new cached configuration is added.