mySQL database user name is too short - 16 chars instead of the (allowed) - 32 mySQL, 80 for maria

32 started at least with mySQL 5.7: https://dev.mysql.com/doc/refman/5.7/en/user-names.html which served starting 2015 and is now EOS

MariaDB 10 has 80 since 2013: https://jira.mariadb.org/browse/MDEV-4332

I suggest changing to 32 chars at least; ideally, ispconfig would have a flag for mySQL/MariaDB in the server settings, similar to apache/nginx