Add custom headers or authentication to HTTP provider for traefik

Question

I'd like to use traefik V2's built-in HTTP provider to dynamically get routing configurations. However, traefik does not seem to have an option to provide authentication to those HTTP endpoints. This means that the HTTP endpoint needs to be public, which is not something I think is very secure.

The only settings I could find are

endpoint
pollInterval
pollTimeout
tls

Am I missing something, or is it really not possible to add for example API key headers to the HTTP provider of traefik v2?

The alternative I'm considering now is building a custom provider plugin, but this seems like overkill.

I've tried to search online for ways that other people have solved the problem, but noone seems to encounter the same problem.