@dbanty Anything else I can help test with this MR?

@johnthagen I totally lost track of this PR, sorry! I think that the logic is now roughly the same as what it was in 0.16 and prior. However, I'm realizing that encoding None as a string is almost definitely the wrong behavior. I haven't actually used multipart in many years at this point—are you aware of a convention for sending a literal null? Should we just be omitting the value like we do for query params?

Since this version is strictly better than what's before it (and I think really close to 0.16), I'm going to merge as-is. We can address passing nulls via multipart once someone reports a real-world need for it.

@dbanty Thanks and I think your plan sounds great! I'll also test the 0.20 release and report back to you.

@dbanty Confirmed that 0.20.0 resolved #926 and everything else appears to be working fine with it too. Thanks!