use copy and unlink instead of rename. Might be universally the better option for all environments (i.e. NFS)

updating the website title by the cronjob shouldn't be necessary as it should get updated by the server plugin

Generate always new key 
use rsa 4096 like in certbot

nginx_plugin: delete statistic generator configuration files if they have been changed to something else

apache2_plugin: delete statistic generator configuration files if they have been changed to something else

Cron logs are in the private directory, not in log directory