* Add support for admission webhook warnings.
This extends `apis.FieldError` to support designating certain FieldErrors as "warnings" (or explicitly as "errors", however, this is the default for back-compat).
You can turn an `apis.FieldError` into a warning using: `fe.At(apis.WarningLevel)` or force it into an error using: `fe.At(apis.ErrorLevel)`.
You can get the errors at a particular diagnostic level using: `fe.Filter(apis.WarningLevel)`.
This change also hooks this into the admission webhook infrastructure to support surfacing the "warning" level `apis.FieldError`s via the `Warnings` section of the `AdmissionResponse`.
Fixes: #2497
* Add a comment about the use of defer.
* have simple tests. working on impl.
* strict setting, reflection based.
* ran codegen.
* adding license.
* update based on feedback and merge better.
* getting closer to something simpler assuming shallow reflect.
* adding validation test.
* use the json tag.
* Golang things nil typed pointers are not nil.
* Use real value of reflect invalid.
* add a missing test.
* two methods, one for update, one for single check.
* checkdep is now in apis.
* fix pkg.
* Update apis/deprecated_test.go
Co-Authored-By: n3wscott <32305648+n3wscott@users.noreply.github.com>
* add code clarity.
* include inlined struct objects recursively.
* Update commnets and add a flatten error test for inlined.
Dave Protasowski
Matt Moore
Markus Thömmes
Victor Agababov
Scott Nichols