apache is just what we are using the provide a front facing web page and you cannot set that kind of custom header on a request.
MVIS is the backend API / server which is where the CORS issue is. I was asking if there was a way to do what you are suggesting thinking there would be some sort of config file I couldn't find in the doco where we could add in custom headers.
Nb. Since creating this question I have logged a support ticket with Rocket and they have responded that it is currently unable to do it and it is with development. They did suggest some workarounds which was to setup a proxy and call that instead and for that to deal with CORS issuehttps://medium.com/@dtkatz/3-ways-to-fix-the-cors-error-and-how-access-control-allow-origin-works-d97d55946d9https://gist.github.com/jesperorb/6ca596217c8dfba237744966c2b5ab1e
As we were developing with apache we have currently gone with this (until there is fix/update to MVIS)https://chriscarey.com/blog/2014/06/13/apache-proxy-with-cors-headers/