Fixed: WARNING - assumed 'LOGLEVEL_WARNING' (this will throw an Error in a future version of PHP) in /usr/local/ispconfig/server/lib/classes/services.inc.php on line 44

Preserve body structure in send_notification_email

Add new file 100-monitor_kernel_version.inc.php to stable-3.1 in relation to recently merged commits of ispconfig/ispconfig3!790 and ispconfig/ispconfig3!791.

There is a fix to the filename for master submitted via commit ispconfig/ispconfig3!804 that is still pending.

Update letsencrypt.inc.php as per the discussion at ispconfig/ispconfig3#5030. Already pr'ed and merged in master via ispconfig/ispconfig3!778. Perhaps can be merged with stable too?

Added a third parameter to $app->log() function in server part to turn off logging to database and use this option in mysql lib to not log any server side SQL errors to the database.