Each receipt or warranty is rendered in the language of the store it was issued in. But if we do not know the store language (e.g. if it was an Online-Store) the given fallbackLang is used.
Note that this parameter is ignored if the language is know and if not ignored it changes only static texts, not e.g. product names.
Allowed values:defrit
Default:de
Type of generated output HTML, PDF
Note that the Accept HTTP header of the request is ignored and
the format must be selected via this query parameter.
Allowed values:htmlpdf
Default:html