Feature: #33071 - Add the http header "Content-Language" when rendering a page

See forge#33071

Description

By default a header "Content-language: XX" is sent where "XX" is the iso code of the sys_language_content (in the sys_language record, it is represented by the sys_language_isocode field), if that is properly defined by the sys_language record representing the sys_language_uid. Setting "config.disableLanguageHeader" disables that.

Impact

By default in new and existing installations a header "Content-language: XX" is sent where "XX" is the iso code of the sys_language_content if that is properly defined by the sys_language record representing the sys_language_uid. You must set "config.disableLanguageHeader" to disable that and get previous behavior (no header).