Add option to specify DNS used to resolve host names for acme provisioner

[ionrover2]

What would you like to be added

I would like the option to specify a specific dns server to resolve host names for an acme provisioner.

Why this is needed

I have 4 large lab isolated environments sharing the same root CA, but hostnames are not unique to each environment. It would be ideal to run a single instance of step with multiple ACME provisioner endpoints that use the appropriate dns server for n number of zones that I have.

[dopey]

Hey @ionrover2, thanks for opening the issue. We agree that ideally you could run different dns resolvers per ACME provisioner. There's a flag that you can pass to step-ca to select the resolver but it sets the resolver for the entire process.

Unfortunately, we don't have the resources to address this issue right now. I'll add it to our roadmap and we'll let you know when we are able to prioritize it. In the mean time if anyone from the community would like to take a crack at adding this configuration to the ACME provisioner, let us know and we'll gladly give some guidance.