[NET-11256] Add gateway read command to consul-k8s CLI

[nathancoleman]

Note

This PR is blocked by the bug fix in #4434 which is preventing tests from passing

Changes proposed in this PR

This PR adds a new command, consul-k8s gateway read, which collects the various components of configuration for a given Consul API Gateway – Gateway, attached HTTPRoutes, attached TCPRoutes, etc. – into a single yaml file.

It can output an archive named after the read gateway into the current directory, or it can output JSON to the terminal.

# Output a zip archive for my-gateway in the current namespace on your kubecontext
$ consul-k8s gateway read my-gateway --output archive

# Output JSON to the terminal for my-gateway in the <my-namespace> namespace
$ consul-k8s gateway read my-gateway --namespace my-namespace --output json

How I've tested this PR

Create one or more Gateways in your Kube cluster. Example for this config is available here.

Run the commands above to inspect the various forms of output, making sure to use both the implicit namespace on your kubecontext and an explicit --namespace <my-namespace> arg.

How I expect reviewers to test this PR

See above

Checklist

• Tests added
• CHANGELOG entry added

[jm96441n]

should we notify that the default value for this is the default namespace

[jm96441n]

and should we clarify that it's the k8s namespace and not the consul namespace (in case they do some mapping of namespaces?)

[nathancoleman]

the default value is whatever namespace is set on the kubecontext, so it could be default or it could be something else

[jm96441n]

did we mean to bump the toolchain here? it's probably good that we do (and should probably be on the latest minor version tbh)

[nathancoleman]

I did not mean to -- I must be running a newer version of Go on my machine than what we use in the repo.

I'll bump it back down just to avoid sprawl in this PR

[jm96441n]

is it possible that someone is running the v1alpha1 of the gateway if they're on an old consul-k8s version? should we worry about that/care about that?

[nathancoleman]

v1.2 which introduced Gateway to consul-k8s itself consumes v1beta1.Gateway here, so customers would have to be using the old standalone consul-api-gateway project in order to be running the v1alpha1.Gateway.

Based on that, I don't think we need to support it here.