Core API: Exact PathMatch

[kate-osborn]

Support Exact PathMatchType in HTTPRoute resource. See https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1beta1.PathMatchType

Acceptance criteria:

• Implement exact matching
• Ensure NKG rejects any values invalid for NGINX
• Ensure a test based on this https://github.com/kubernetes-sigs/gateway-api/blob/7631139b1ea4beaf575a49f56c56aa26f1e11e22/conformance/tests/httproute-exact-path-matching.go#L33 can pass
• Ensure if two rules have the same path (one rule has prefix matching and one has exact matching), matching works as expected (see below)
• Ensure that if two rules have the same exact path but have different matches based on headers or other request params, matching works as expected.
• Update the doc https://github.com/nginxinc/nginx-kubernetes-gateway/blob/main/docs/gateway-api-compatibility.md

Appendix:
Two locations with the same path but different matching (exact and prefix)

    location = /hello {
        return 200 "exact hello\n";
    }

    location /hello {
        return 200 "prefix hello\n";
    }

curl localhost:8090/hello
exact hello

curl localhost:8090/hello/abc
prefix hello

Aha! Link: https://nginx.aha.io/features/NKG-60

[sjberman]

When we say "if two rules have the same path", does this consist of two separate rules, or two separate matches within a rule, or both?

[pleshakov]

@sjberman

When we say "if two rules have the same path", does this consist of two separate rules, or two separate matches within a rule, or both?

two separate rules

however, two separate matches within a rule could be a good case to also check.