add version and headers fields to HTTPChk

[kenichi-mashiyama]

Summary

This PR adds support for custom HTTP versions and HTTP headers in the HTTPChk configuration for backends and listens.

Motivation

Currently, spec.httpchk only supports method and uri fields, which limits the ability to construct custom http-check send directives (e.g., option httpchk GET / HTTP/1.0\r\nUser-Agent:...).

By adding the optional version and headers fields to HTTPChk, users can now set custom HTTP versions (such as HTTP/1.0) and append arbitrary headers (like custom User-Agents) to their health check requests.

Changes

• Added version and headers fields to the HTTPChk struct in apis/config/v1alpha1/common_types.go.
• Implemented HasCustomSendLine() and CustomSendHTTPCheck() helper methods to build the appropriate http-check send directive when version or headers are set.
• Updated AddToParser() in backend_types.go to inject the custom http-check line into the HAProxy configuration.
• Regenerated CRDs, DeepCopy methods, and API documentation.
• Added unit tests in backend_types_test.go to verify custom http-check send generation and validation logic.

Checklist

• Code changes implemented
• Unit tests added/updated
• Generated CRDs and API docs updated

[m-terra]

LGTM - thank you very much for your contribution

[xosk31]

Thanks for the contribution, much appreciated!