Motivation:
if enableQuota is true, mail plugins cannot be enabled in extraConfig
because of the problem described here:
https://doc.dovecot.org/configuration_manual/config_file/config_file_syntax/#variable-expansion
doveconf: Warning: /etc/dovecot/dovecot.conf line 8: Global setting
mail_plugins won't change the setting inside an earlier filter at
/etc/dovecot/dovecot.conf line 5 (if this is intentional, avoid this
warning by moving the global setting before /etc/dovecot/dovecot.conf
line 5)