reverseproxy: allow user to define source address

[mohammed90]

TODO:

• Caddyfile support

Closes #6503

[mohammed90]

This failure appears to be legit because it fails even locally for me, though not related to this PR

https://github.com/caddyserver/caddy/actions/runs/10331386719/job/28601743464?pr=6504#step:3:4268

Edit: git bisect identifies 59cbb2c as the bad commit.

[francislavoie]

I think users might want to use an interface name instead of an IP as well, we'd likely want to support that too? I've had this owasp-amass/amass@f5c3960 bookmarked for a long time as a reference for how to do that.

[mohammed90]

I think users might want to use an interface name instead of an IP as well, we'd likely want to support that too? I've had this owasp-amass/amass@f5c3960 bookmarked for a long time as a reference for how to do that.

I'd solve that differently. We can use the new RegisterNetwork function to register a network called interface processing a network address looking like this, e.g.: interface/eth0:port. Then the implementation in this PR inherits the utility by default. What do you think?