Genericize PartialObjectMeta over the underlying Resource

[clux]

Allows doing static dispatch using the root type, and avoids having to do stringly typed oob signalling in generic code.

Fixes #1151, in particular:

• Adds a serde skipped + defaulted PhantomType<K> to PartialObjectMeta
• Fixes broken Resource impl for PartialObjectMeta by instead proxying to K: Resource
• I.e. all usage of PartialObjectMeta has changed to PartialObjectMeta<K>
• Still works dynamically via PartialObjectMeta<DynamicObject> (which it is inferred to in dynamic_watcher)
• Fixes up extension names in metadata api in core_methods used for tracing
• Adds a converter trait PartialObjectMetaExt from ObjectMeta into PartialObjectMeta<K>

Example generic code:

pub async fn reconcile<K>(obj: Arc<PartialObjectMeta<K>>, ctx: Arc<Context>) -> Result<Action>
where
    K: Resource<Scope = NamespaceResourceScope, DynamicType = ()>
        + Clone
        + DeserializeOwned
        + Debug,
{
    let kind = K::kind(&()).to_string();
    let api: Api<PartialObjectMeta<K>> = Api::default_namespaced(ctx.client.clone());

This now gives us a way to get type info in generic code without extra ApiResource args and lambdas, while also maintaining all the static type safety we have around scopes.

[codecov-commenter]

Codecov Report

Merging #1152 (c228fb6) into main (825aba8) will increase coverage by 0.30%.
The diff coverage is 86.84%.

❗ Current head c228fb6 differs from pull request most recent head 1ecb6ec. Consider uploading reports for the commit 1ecb6ec to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1152      +/-   ##
==========================================
+ Coverage   72.26%   72.57%   +0.30%     
==========================================
  Files          67       67              
  Lines        5106     5123      +17     
==========================================
+ Hits         3690     3718      +28     
+ Misses       1416     1405      -11     

Impacted Files	Coverage Δ
kube-client/src/api/mod.rs	68.75% <ø> (ø)
kube-runtime/src/watcher.rs	41.50% <ø> (ø)
kube-client/src/api/core_methods.rs	71.83% <72.72%> (ø)
kube-core/src/metadata.rs	85.71% <91.66%> (+70.32%)	⬆️
kube-client/src/lib.rs	93.95% <100.00%> (+0.06%)	⬆️
kube-core/src/resource.rs	58.33% <0.00%> (+4.76%)	⬆️

[clux]

cc @mateiidavid

[nightkr]

LGTM overall. I'm starting to wonder if this would let us remove the dedicated Api::*_metadata methods and just infer that based on K, but that's probably a question for another time.

[nightkr]

Is this a valid thing in general, or do we want to make it a dedicated associated function where we can call out any caveats? Should we take the TypeMeta from K instead of making up our own?

[clux]

Ugh, this was a really good call. Thank you. The From is way too simplistic here because how we want to use PartialObjectMeta depends on whether it is a request object or a response object (the apiserver erases the type, but the root type is needed for patch).

Have removed the From and instead created a sealed PartialObjectMetaExt trait that contains two converter functions, and have used it in the main test case.