Add engine.NewWithClient func

[object88]

closes #8725

Signed-off-by: Paul Brousseau object88@gmail.com

What this PR does / why we need it:

Special notes for your reviewer:

If applicable:

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

[bacongobbler]

hi @object88. Generally speaking we ask contributors to provide tests along with their PRs to ensure things are tested.

Have you played around with this PR yet? What do you think about the design? As it stands, right now you have to instantiate the Engine before setting the Strict flag:

e := engine.NewWithClient(client)
e.Strict = true

Perhaps there's a better way to improve the design here. What do you think?

[bacongobbler]

I'm wondering maybe instead of a NewWithClient, perhaps a new function called func (e *Engine) UseConfig(config *rest.Config) might be slightly better here.

e := Engine{Strict: true, LintMode: true}
e.UseConfig(config)

Happy to hear your thoughts on this one. I don't think we want to make config public after the engine has been instantiated so it cannot be accessed and re-used for another purpose... Seems like poor design for an engine to expose credentials that should not be accessible or usable to the caller.

[object88]

Personally, I love using Option funcs pattern, and I see that's in use in the getter package. The engine package doesn't have as many properties to contend with, but I find that it's a good way to ensure that one can expand later. And it allows properties to be kept private (and concurrency-safe, which UseConfig may not, on an assumption).

It wasn't terribly obvious to be what unit tests would be meaningful for the initial PR. But rewriting this with a New(opts ...OptionFunc) to set config, strict, etc., properties would certainly call for it.

[object88]

Sorry for the delays in this; setting to draft while I get to reimplementing.