docs(gateway): Add route ordering/priority guidance (group.order equivalent)

[GiladTrachtenberg]

Describe the feature you are requesting

Add documentation for Gateway API that explains how to achieve route ordering/priority behavior equivalent to the alb.ingress.kubernetes.io/group.order annotation available for Ingress resources.

Motivation

Users migrating from Ingress to Gateway API lose the ability to explicitly control rule evaluation order using group.order. The current Gateway API documentation doesn't address:

1. How the controller determines rule priority when multiple HTTPRoutes attach to the same Gateway listener
2. Whether the ListenerRuleConfiguration CRD can be used to set explicit rule priorities
3. Best practices for achieving deterministic rule ordering across multiple HTTPRoutes
4. Migration guidance for users who relied heavily on group.order for complex routing scenarios

This is a common pattern in multi-team environments where different teams own different HTTPRoutes but need predictable rule precedence (e.g., ensuring a catch-all route from one team doesn't shadow more specific routes from another team).

Describe the proposed solution you'd like

Add a section to the Gateway API documentation (potentially under docs/guide/gateway/) that covers:

1. Rule precedence behavior: How the LBC determines ALB listener rule priority when reconciling multiple HTTPRoutes
2. Explicit priority control: Whether a priority field exists or is planned for ListenerRuleConfiguration (similar to how Ingress uses group.order)
3. Workarounds: Patterns for achieving predictable ordering using path specificity, match conditions, or route consolidation
4. Migration guide: A mapping table showing Ingress annotation patterns and their Gateway API equivalents, specifically addressing group.order

Describe alternatives you've considered

• Opening a feature request for adding a priority field to ListenerRuleConfiguration or as an annotation on HTTPRoute (if explicit ordering isn't currently supported)
• Relying solely on Gateway API spec's implicit precedence rules (path specificity, hostname matching), though this may not cover all use cases

Contribution Intention (Optional)

• Yes, I am willing to contribute a PR to implement this feature
• No, I cannot work on a PR at this time

[shuqz]

hi,
Thanks for reaching out.

How the controller determines rule priority when multiple HTTPRoutes attach to the same Gateway listener

We follow standard instructions from gateway api to decide precedence order. For example, "Exact" path match will always have higher precedence than "Prefix" path match. Path with exact value will have higher precedence than path with wildcard etc. See all details in this file. And it should always come up with an order.

At this point we are not thinking to support group.order since it will not align with gateway api instruction. Can you elaborate with example of an uncovered use case?