Motivation / Background

Using unprocessable_entity will emit a warning on Rack 3.2

This to me seems like the least invasive change and is also how headers are currently handled.

There's some code in jbuilder that will need a similar change. https://github.com/search?q=org%3Arails+unprocessable_entity+-repo%3Arails%2Frails&type=code. I will take a look if this is accepted.

Question: Should ActionDispatch::Constants be nodoc? I think it should be but can that just be done now after it's been availale for a year?

cc @ioquatix

Additional information

There have been various PRs in the past for this:

• Use direct status code to avoid deprecation warnings. #52252
• Use unprocessable_content instead of unprocessable_entity #52192
• Change mapping 422 response status #52087
• Rename unprocessable_entity -> unprocessable_content. #52097

Maybe this will be the one.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.