wai: add getRequestBodyChunk to silence requestBody deprecation warning

[dbeacham]

Before submitting your PR, check that you've:

• Bumped the version number
• Documented new APIs with Haddock markup
• Added @since declarations to the Haddock

After submitting your PR:

• Update the Changelog.md file with a link to your PR
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[Vlix]

Thank you for the PR!

I think the name setRequestBodyChunk makes sense to be the opposite of getRequestBodyChunk, but you're not setting a chunk when using this setter, so I think just keeping it as setRequestBody might be better. Or maybe even replaceRequestBody 🤔

[dbeacham]

Yeah - name could be better. setRequestBodyChunks is another alternative.

[Vlix]

@dbeacham could you add to the conversation in #849 ?

[kazu-yamamoto]

@Vlix This PR looks good to me. May I merge this as is?

[Vlix]

There should be an @since declaration, version bump and addition to the ChangeLog, no?

[dbeacham]

Yeah. I'll sort that out later today.

[kazu-yamamoto]

Rebased and merged.
Thank you all for your contributions!