Document how HTTPProxy route/include match condition precedence works

[sunjayBhatia]

Our request routing page has detail on what the various HTTPProxy route/include match conditions do, but not how they interact, in terms of precedence etc.: https://projectcontour.io/docs/1.26/config/request-routing/#conditions

Since Envoy matches requests against routes it is configured with in the order it is presented them, we sort routes for a given virtualhost based on precedence of the route match conditions that are configured.

This route sorting is performed here: https://github.com/projectcontour/contour/blob/main/internal/sorter/sorter.go#L286-L295

We should do a better job of documenting this so it is less ambiguous for HTTPProxy users. Namely we should mention that specificity of route match conditions determine the order that matches will occur:

• Exact matches come first
• Regex matches come next, ordered by expression length (as a proxy for specificity)
• Prefix matches come next, ordered by length
• If there is a tie, header matches are evaluated
• If there is still a tie, query param matches are evaluated

Notes:

• Came out of: https://github.com/projectcontour/contour/issues/5773
• Gateway API has a nice specification here that is pretty similar to how Contour works already: https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io%2fv1beta1.HTTPRouteRule

[AHB102]

I am new to open source, can I start contributing from this issue?

[Garvit-77]

@sunjayBhatia Could you assign this issue i would like to work on it.