Add PINNIPED_SKIP_PRINT_LOGIN_URL env var to CLI

[cfryanr]

The approach taken in #1874 to attempt to solve #1868 did not work as well as I had hoped.

This PR removes some of the code from #1874 and replaces it with a new env var used by the CLI called PINNIPED_SKIP_PRINT_LOGIN_URL, which causes the CLI to skip printing the login URL to stderr when the env car is set to true and when the browser was opened to the login URL.

For example, you could use PINNIPED_SKIP_PRINT_LOGIN_URL=true k9s --kubeconfig pinniped-browser-flow-kubeconfig.yaml to start k9s.

Release note:

The `pinniped login oidc` CLI command will skip printing the login URL to stderr if the browser has successfully opened and if the `PINNIPED_SKIP_PRINT_LOGIN_URL` env var is set to `true`. This new env var can be used to avoid having the URL output on stdout confuse console UIs like k9s.

[codecov]

Codecov Report

Attention: Patch coverage is 58.33333% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 38.25%. Comparing base (15627e7) to head (92a082b).

Files	Patch %	Lines
pkg/oidcclient/login.go	16.66%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1897   +/-   ##
=======================================
  Coverage   38.25%   38.25%           
=======================================
  Files         347      347           
  Lines       44200    44207    +7     
=======================================
+ Hits        16907    16910    +3     
- Misses      26780    26785    +5     
+ Partials      513      512    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[joshuatcasey]

Could this be a pinniped CLI argument, so that it could be baked into a kubeconfig? Would we want that? I guess the same kubeconfig would be used for both kubectl and k9s, so that isn't really desirable.

[joshuatcasey]

Should we relax this a bit to allow for True or TRUE? The following func should only return true for a very limited number of values as per https://gosamples.dev/string-to-bool/. We could still document using true but this allows for variations.

func isTruthyString(s string) bool {
	b, err := strconv.ParseBool(s)
	return err == nil && b
}

[cfryanr]

We can do that if you'd like. I was copying the style used by the existing PINNIPED_DEBUG env var which is either true or anything else is considered not true.

[cfryanr]

Could this be a pinniped CLI argument, so that it could be baked into a kubeconfig? Would we want that? I guess the same kubeconfig would be used for both kubectl and k9s, so that isn't really desirable.

It could be a flag. The community member who reported this problem suggested that as a solution. However, I was thinking the same thing that you mentioned about the same kubeconfig being used for both purposes, which is why I thought maybe it should be an env var.

If a user wanted to hardcode this value into their kubeconfig, they can still do so, because you can put env var names and values into the kubeconfig (see https://kubernetes.io/docs/reference/access-authn-authz/authentication/#configuration).