As discussed in https://github.com/theforeman/foreman/pull/7909

The HTTP header names used for Apache SSO are hardcoded in

app/services/sso/apache.rb

In many other projects the names of http headers for this purpose is user configurable to offer flexibility in regard to the many different types of apache auth modules that exists. For example the 'mod_auth_cas' Apache module sets its own http headers for mail/lastname/givenname, with different names than those set in 'apache.rb'.