Inference Extension: Documentation

[sjberman]

As a user, I want to know how to use NGF with the inference extension, so I can route traffic intelligently to my AI workloads in Kubernetes.

Acceptance Criteria:

• Add a user guide on how to route traffic to AI workloads using NGF
• Should cover how to install the Gateway API Inference Extension CRDs, and deploy NGF with the feature flag enabled
• Should cover how to deploy an InferencePool and EPP, and how to configure an HTTPRoute to reference the InferencePool
• Explain how to secure traffic between the NGINX pod and the EPP using cert-manager (mentioning that by default, we create self-signed certs)
• Link to Gateway API inference extension docs where it makes sense (for example, these docs may better describe the InferenceObjective CRD and how a user should handle those)

Additional acceptance criteria update:

• Legal text specifying NGF is not responsible for any threats or risks associated with using a third-party EPP.
• Document insecure gRPC connection shortfall, and how the gateway inference is in Alpha and should not be used in production environments.