[cryptpad] allow for a correct configuration

[iMartyn]

Details

Helm chart name: cryptpad

Describe the solution you'd like: I'd like to configure cryptpad correctly using two ingress objects pointing at two services, where one is listening in the container on a separate port.

Even with additionalServices and additionalIngresses this isn't possible because the common template class doesn't support overriding of the backend.

Anything else you would like to add:

cryptpad listens on two ports (by default 3000 and 3001) and expects them to be accessible by two domains. Using nginx-ingress I can do almost everything (although lots of stuff in values.yaml that should be IMO abstracted away) but the final step of sending ingress traffic for the second domain to the other service isn't possible with the current template.

Additional Information:

https://github.com/nicholaswilde/helm-charts/blob/becc0763594d40bc22efc8ac979cfc9b424fefe8/charts/common/templates/classes/_ingress.tpl#L17 hardcodes the servicename so you cannot point at a service that is created with additionalServices