How to apply X-Forwarded-Proto https to specific client

See these pages, as they have all information about what you need:

https://devcentral.f5.com/wiki/irules.class.ashx

https://devcentral.f5.com/wiki/irules.http__header.ashx

You need a datagroup to define the users IPs for the new service, and to add the header. Something like this, not tested, just copied from those solutions:

when HTTP_REQUEST {
    if { [class match [IP::client_addr] equals "localusers_dg" ] } {
        HTTP::header insert "X-Forwarded-Proto" "https"
    }
}