add PodSecurityPolicy removal note in docs

[BBBmau]

Description

Fixes #2234

Acceptance tests

• Have you added an acceptance test for the functionality being added?
• Have you run the acceptance tests on this branch?

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccXXX'

...

Release Note

Release note for CHANGELOG:

...

References

Community Note

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[jrhouston]

Perhaps we should also set a DeprecationMessage in the schema for this resource, as we will want to remove this in a future major version of the provider.

[alexsomesan]

+1 to what @jrhouston said. We should to surface the deprecation to users at runtime. Ideally we also gate the use of this resource on the API server version. We have precedent of that in some other resources.

[arybolovlev]

I would add my 5 cents here.

This is not the only resource that got deprecated in this or that Kubernetes version, we have a few of them. I would vote for a more standardized approach. We could have a section in our documentation on top that mentions the target Kubernetes release of the resource that gets deprecated. Usually, this information is available a few releases in advance. It also would be nice to mention whether there is a successor resource in our provide if applicable, so practitioners can plan migration ahead. And this all should be synchronized with the resources warning messages.

I think it could be a part of the documentation improvement epic, along with the kind and API versions that the resource implements.

[jrhouston]

Follow up discussion: instead of DeprecationMessage we should check the cluster version and:

1. If the version is 1.21+ return a warning diagnostic saying the resource has been deprecated
2. if the version is 1.25+ return an error saying the resource cannot be used on cluster versions 1.25+