Add example for raw API Server requests

[mateiidavid]

Motivation

I noticed a couple of questions around querying the metrics API that a kubelet exposes. A number of different use cases aside from stat queries may require raw requests to the API Server (in the style of kubectl get --raw).

It does not make much sense to extend the Request API to cover this use case (since an abstraction would not simplify anything). Users can, however, make use of the http::Request type and use an instantiated client to interface with the API Server. There's a lack of material here, so I thought I'd include an example that other people may reference.

Solution

The example builds the equivalent of kubectl top nodes (in a simpler, and dumber way) using raw HTTP requests. The data may not be as exact as what kubectl top offers, but it serves as an example on how data may be queried.

If this isn't needed, I'm happy to put it in a gist somewhere, no time wasted so no worries there :) It is an unsolicited PR.

:; kubectl top node
NAME                  CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%
k3d-agent-0-0         34m          0%     65Mi            0%
k3d-source-server-0   168m         1%     1516Mi          4%



:; cargo run -p kube-examples --example request_raw
NAME                    MEMORY(bytes)     MEMORY%   CPU(cores)   CPU%
k3d-source-server-0     1914Mi            6%        195m         1%
k3d-agent-0-0           60Mi              0%        67m          0%

[codecov]

Codecov Report

Merging #1330 (44980d4) into main (9c81f1f) will decrease coverage by 0.2%.
Report is 4 commits behind head on main.
The diff coverage is n/a.

❗ Current head 44980d4 differs from pull request most recent head a3a7f43. Consider uploading reports for the commit a3a7f43 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1330     +/-   ##
=======================================
- Coverage   72.4%   72.1%   -0.2%     
=======================================
  Files         75      75             
  Lines       6343    6377     +34     
=======================================
+ Hits        4586    4597     +11     
- Misses      1757    1780     +23     

see 5 files with indirect coverage changes

[clux]

thanks for this, saw you were providing helpful answers.

i like this example, it's advanced enough to be useful, and not too complicated either.

there are a few nits i've suggested to make it more readable, but this is definitely parseable.

[clux]

Thanks a lot!