@brief server default language for sorting strings
`--default-language default-language`

The default language ist used for sorting and comparing strings.
The language value is a two-letter language code (ISO-639) or it is
composed by a two-letter language code with and a two letter country code
(ISO-3166). Valid languages are "de", "en", "en_US" or "en_UK".

The default default-language is set to be the system locale on that
platform.