See associated ticket for details on how this patch is meant to be used.

FWIW, @manutter51 independently confirmed that this patch worked

@pyrmont The inelegant use of str->bytes and vector construction in this PR has bothered me, but I haven't thought of a cleaner way to write this, so putting it in for review.

Oh, I see that I haven't added any associated documentation for this change. Let me do that.

Rebaselined via force-push.

OK, even though the documentation is thin, we may be OK. We have the fact that :body can be binary:

(s/def ::body (s/or :string string? :binary vector?))

and in the :multipart-params portion of the docstring it has:

can be a string or a vector of unsigned bytes (binary)