Admission Control: support per route config

**QUESTION: Admission Control Non-Global Configurations**

*Description*:
When I try to configure Admission Control for a specific route I get the error that `The filter envoy.filters.http.admission_control doesn't support virtual host-specific configurations`.

I'm trying to understand the limits of this. Could I for example split traffic on headers and apply Admission Control to one set of headers? I'm still getting my bearings in the codebase, but I think this wouldn't be possible, right?

What would the complexity (and interest) be in a patch to make this filter available for virtual host-specific configurations, ex. for different headers, or different subpaths.

Thank you,