Add socket support

Enable socket communication for the suggested Nextcloud config using the community.general.redis module, the Debian defaults from /etc/redis/redis.conf are:

# Unix socket.
#
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /run/redis/redis-server.sock
# unixsocketperm 700