fix(config): keep the category cache in the memory cache when available

A cache belongs in Nextcloud's memory cache rather than in the app
config. Use the distributed cache (e.g. Redis) with a one-week TTL when
one is available; Nextcloud falls back to the local cache (APCu) when
only that is configured. Without any memory cache the lazy app config
value stays as the fallback. A leftover app config value is removed
when the categories are stored in the memory cache, and saving the
settings clears both.

lib/AppInfo/Application.php

@@ -21,6 +21,7 @@ use OCP\AppFramework\Bootstrap\IRegistrationContext;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\IAppConfig;
+use OCP\ICacheFactory;
 use OCP\IConfig;
 use OCP\INavigationManager;
 use OCP\IRequest;
@@ -62,7 +63,8 @@ class Application extends App implements IBootstrap
                 $c->get(IUserSession::class),
                 $c->get(IAppConfig::class),
                 $c->get(ITimeFactory::class),
-                $c->get(LangRepository::class)
+                $c->get(LangRepository::class),
+                $c->get(ICacheFactory::class)
             );
         });