Is your feature request related to a problem? Please describe.

We have several cli applications that communicate over HTTP, and we would love to use pomerium for these as pomerium provides loads of logging, auditing, AAA, and also allows for injection of mTLS and headers. It is amazing and we love it!

One of the features I recently learned about was the "programmatic access" function of pomerium whereby you can add a specific Authorization header and it will authenticate past pomerium for non browser environments. This is exactly what we need! But unfortunately these CLI applications only allow certain things to be added (for example they allow for a basic auth username and password to be supplied). Would it be possible to also allow for "basic auth" to be used instead of just the

"Authorization: Pomerium a.real.jwt"

For example the username could be a static "pomerium" and the password could be the JWT. This is also how some other sites do it with API keys (i.e. the API key is the password of a basic auth and the username is some static thing like "api")

Describe alternatives you've considered
We thought about writing our own proxy but I think it would be nicer to have in Pomerium itself

Explain any additional use-cases
Basically, for "legacy" or static applications that do not support adding any additional headers past basic auth (as basic auth is very well adopted)

Additional context

Add any other context or screenshots about the feature request here.