Allow `StartupProbe` to be configured via helm

[shaun-nx]

Is your feature request related to a problem? Please describe.

User would like to configured their backend application with a health check before the pod starts

Problem definition:

• Bad config ingress is applied to a running Nginx Ingress Pod.
• Bad could be just a snippet that is not correct, even just missing a semi-column ( see attached example )
• Ingress Pod continues working.
• Ingress Pod fails is restarted or replaced
• No configuration is being loaded but the readiness probes is successful

Describe the solution you'd like
I would like to be able to configure a StartupProbe for the Ingress Controller. I need to be confident that the /etc/nginx/conf.d/ directory was created successfully upon pod restart

Describe alternatives you've considered
Right now, we create dummy ingress that listens on a different port ( in our example 9999 ) and always responds with 200 OK and have pointed the readiness probe to this port.
Since this dummy ingress is part of the conf.d it will fail also when the configuration is loaded at startup and therefor the probs will fail.

[github-actions]

Hi @shaun-nx thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this 🙂

Cheers!