fix(kuma-cp): change way of setting if resource is read only (backport #5345)

[mergify]

This is an automatic backport of pull request #5345 done by Mergify.
Cherry-pick of dd2a67d has failed:

On branch mergify/bp/release-2.0/pr-5345
Your branch is up to date with 'origin/release-2.0'.

You are currently cherry-picking commit dd2a67dfd.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   pkg/api-server/resource_endpoints.go
	new file:   pkg/api-server/server_test.go
	modified:   pkg/core/resources/model/resource.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   pkg/api-server/server.go

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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