Fix hardcoded controller class

[mikhno-s]

Add flag nginx-class, which can be set specific class for running multiple nginx ingress controllers.

[pleshakov]

@SiriusRed thanks!

A couple of suggestions:

• This PR breaks the current behavior, which is described here . Currently, Ingress resources with the annotation kubernetes.io/ingress.class: "nginx" or no annotation are handled by NGINX Ingress controller. It is better not to change this behavior. If you would like to make the Ingress controller process only Ingress resources with the annotation kubernetes.io/ingress.class: "nginx", I suggest to have an additional Boolean command-line flag, something like ingress-class-only.
• It is better to rename the flag from nginx-class to ingress-class

[mikhno-s]

Thanks for remark, mr. @pleshakov!

• Renamed the flag nginx-class to ingress-class, it is more clearly.
• Add flag 'use-ingress-class-only' for handled ingresses only with matching value of 'ingress-class'.

[pleshakov]

Thanks @SiriusRed

I have a few additional suggestions:

• Could you change VERSION in the Makefile from 1.0.1 to 1.0.0. We only change VERSION, when we make a new release?
• Could you run all modified go files through go fmt tool to fix formatting?
• Could you squash all your commits into one commit?

Also, there is a bug. When use-ingress-class-only option is enabled, if an Ingress resource doesn't have the ingress.class annotation, the Ingress controller processes this Ingress resource. It should not process such an Ingress resource, but only Ingress resources for the configured Ingress class.

[mikhno-s]

Thanks @pleshakov for clearly instructions!
Done all of thing which you said. Added comment.

[pleshakov]

@SiriusRed
Thanks. Works as expected now!

Could you make one last change - rename the variables useIngressClass to useIngressClassOnly? This will help make the code more readable.

[mikhno-s]

@pleshakov
Done!

[pleshakov]

@SiriusRed Thanks!