Route Matching during filter dispatch

At present envoy does not support route matching to selectively dispatch a filter.

Nginx/Apache support configs like the following

<Location "/super-secret">
    AuthBasicProvider ldap
   AuthLDAPURL ldap://127.0.0.1/dc=example,dc=com?uid?one
    Require valid-user
</Location>

This config uses the ldap filter only when a route is matched. At present every filter must support an ad-hoc enable-disable flag. This should be supported directly.

Options:

• Add RouteMatch to HTTPFilter
• Standardize on request dynamic metadata key such as filter_name.enabled. This metadata can then be added as part of a route. httpConnectionManager should check this value before dispatching.