[Catalyst] Setting an environment variable with the value of a header

[Robert Rothenberg]

I've not gotten replies to my posts regarding HTTP authentication, so I'm
starting a separate thread.

I am running a Catalyst app as a separate server with a reverse proxy.

If I pass the REMOTE_USER to the Catalyst app via a header such as
X-Proxy-REMOTE_USER, how do I set the REMOTE_USER value for in the Catalyst app?

I've tried looking at Plack settings, but haven't figured out how to do this.

(Another, perhaps easier alternative, is to write a
Catalyst::Authentication::Credential plugin that does this, but I assume
this isn't so unusual that it's already been done. Has it?)