NGF: User guide for session persistence

[salonichf5]

Proposed changes

• Includes a user guide for session persistence
• updated upstream settings policy document
• updates gateway compatibility document
• updates nginx plus features list

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[Copilot]

Pull request overview

This PR adds comprehensive documentation for session persistence in NGINX Gateway Fabric, including a new user guide and updates to existing documentation. It explains both NGINX OSS session affinity using ip_hash and NGINX Plus cookie-based session persistence, while also documenting load balancing method configuration through the UpstreamSettingsPolicy resource.

• Adds a new session persistence user guide with practical examples for NGINX OSS and NGINX Plus
• Updates UpstreamSettingsPolicy documentation to include load balancing method configuration
• Updates API reference to reflect new fields and removed obsolete sections
• Updates Gateway API compatibility and NGINX Plus features documentation

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
content/ngf/traffic-management/upstream-settings.md	Added documentation for configuring load balancing methods via UpstreamSettingsPolicy with examples for random two least_time=header and hash consistent methods
content/ngf/traffic-management/session-persistence.md	New comprehensive guide covering session persistence configuration for both NGINX OSS (ip_hash) and NGINX Plus (cookie-based), with working examples
content/ngf/reference/api.md	Updated API reference to include new load balancing fields, removed ObservabilityPolicy section, and updated Gateway API version references from v1alpha2 to v1
content/ngf/overview/nginx-plus.md	Added session persistence and advanced load balancing methods to the list of NGINX Plus features
content/ngf/overview/gateway-api-compatibility.md	Updated to reflect that sessionPersistence is now supported for HTTPRoute and GRPCRoute

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[ADubhlaoich]

Generally LGTM.

Regarding the OSS/Plus split, this document is small enough that separately documenting the different methods on one page is permissible.

If further delineation is necessary due to increasingly divergent instructions as a result of use cases, I can refactor the structure then.

Aside from everything else, you don't need to branch for the docs repo: cutting a branch directly will give you the preview links, which are easier to review.

[bjee19]

nice work! just a couple of comments.

[bjee19]

LGTM, thanks for making the change!