[dev] Clashes between recent mariadb versions and PHP 8 Horde SQL Config

[Ralf Lang]

Recent versions of mariadb don't accept a $conf['sql']['charset'] of 
utf-8 but want either utf8mb3 or utf8mb4. But the same value is also 
used as input for mbstring, mb_convert_encoding in 
/srv/www/horde/vendor/horde/util/lib/Horde/String.php:160

I think the config value should accept both "utf-8" (as before) and 
"utf8mbX" (more precise and expected by recent mariadb). The assumption 
would be that "utf-8" means utf8mb4 which is true everywhere outside SQL 
databases - and creates problems for kronolith/nag users who save events 
from traveling portals and other sources that use unicode icons. And on 
the other hand utf8mbX (and probably some of their friends) should be 
"UTF-8" for mbstring purposes.

Any other suggestions?