Add support for health status uri customisation

[Dean-Coakley]

Proposed changes

Fixes: #721

Allow customisation of health check uri via cli arg.

• Add -health-check-uri cli argument.
• Add controller.healthCheckURI field to helm chart.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch from my own fork

[pleshakov]

@Dean-Coakley thx for the PR!

please see a few comments

additionally, If the configured URI is not a valid NGINX location, the IC must exit reporting an error.

[Rulox]

As @pleshakov says we need validation, other than that lgtm! 👍

[Dean-Coakley]

@pleshakov

If the configured URI is not a valid NGINX location, the IC must exit reporting an error.

Sorry for missing that. Good catch.

Should be ok now.

[pleshakov]

@Dean-Coakley
thx.
I left a suggestion.

Additionally, just realized that the update of the helm chart doc https://github.com/nginxinc/kubernetes-ingress/blob/master/deployments/helm-chart/README.md is missing :( no doc for healthStatusURI param.

Update. sorry, just realized that / should not be allowed as the location, because we have / in the default server config -- https://github.com/nginxinc/kubernetes-ingress/blob/master/internal/configs/version1/nginx-plus.tmpl#L115
Make sure to cover that case. I suggest you also add a unit test for validateLocation

[Rulox]

lgtm once addressed what @pleshakov pointed, approving! 🚀

[pleshakov]

👍