Allow ListQuery to be instantiated.

[ndenev]

I couldn't find another way to instantiate ListQuery from code that uses kubeclient-rs as the fields are private. Instead of making them public, implement simple constructor so it can be used like so:

    let query = ListQuery::new().label_selector("app=my-great-app");
    let pods = kube.pods().namespace("my-namespace").list(Some(&query));

[anowell]

This is basically just an alternate syntax for:

let query = ListQuery::default().label_selector("app=my-great-app");

I should probably document an example of using this to help make it more discoverable, but is there any particular reason this Default merits a new alias and not others?

Personally, I'm wondering if that exact construction will be common enough to merit supporting ListQuery::with_label("app=my-great-app"); or maybe listing could expose APIs more like this:

list_all()
list_with_label(label: &str)
list(query: ListQuery)

I certainly feel like querying based on label far exceeds other queries, but definitely open to opinions.

[ndenev]

You are right, ListQuery::default() works, for some reason I didn't think of it. I think I tried ListQuery{ ..Default::default() } which understandably didn't work because the fields are private.

[anowell]

Cool. I'm gonna close this for now, but if you have any compelling thoughts on the ergonomics of common usage patterns, feel free to open an issue to discuss. Cheers!