Debugging domain fronting access to conjure station

We've set up a domain front for conjure in #40978 (closed), but I'm having trouble using it.

After talking with the conjure developers, they mentioned that the client's address has to be included in an X-Forwarded-For header. I'd like to propose the following debug steps:

• Quickly check to see if there are XFF settings in our fastly config
• Set up another temporary domain front that points to a test registration server that I'll run.