Authenticated Paths for Proxy Provider

**Is your feature request related to a problem? Please describe.**
Currently, we can only configure "Unauthenticated Paths" for a Proxy Provider. This setting allow multiple regexes to check the URL against.
However, there is no way to only protect specific paths.

**Describe the solution you'd like**
Add "Authenticated Paths" option to Proxy Providers or use another regex library which supports negative lookahead.

**Describe alternatives you've considered**
I tried regex negative lookaheads, but authentik outpost are written in golang, which does not support this.

**Additional context**
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