Problem Statement

There are currently three types of HTTPRoute path match:

• Exact - core
• PathPrefix (default) - core
• RegularExpression - implementation-specific

The only reason for RegularExpression to be implementation-specific is the lack of a shared standard for regex.
What's missing here, though, is a real implementation-specific possibility such as the one provided by ingress:
https://github.com/kubernetes/kubernetes/blob/83bb5d570580a3f477737fec5c24ba8fc3554264/pkg/apis/networking/types.go#L546-L550.

Use case

At Kong, we have the need for this kind of path matching as the router can use a custom language that we would like to leverage in HTTPRoutes as well. This can be useful for other implementations as well.