Support binary data in MTOM

[CyBot]

options.data += `${part.body}\r\n--${boundary}${

converted the body data to a string, making it impossible to send binary data

[w666]

Hi @CyBot,

New feature should not be used by default, please make it optional.
New feature requires a test.
Also, please make sure all current tests still work.

And this did not pass lint check, should be fixe as well.

[CyBot]

IMO it should be the default, because currently it's not working correctly. The whole point of MTOM is sending binary data.
As such it's not a new feature, it's a bugfix.
I can write a test when I get around to it

P.S.: I'll look into the failing test

[CyBot]

The feature that is breaking the test now was not working.
In the test, a readStream is created and passed as the body. All that was put into the request was [object Object].
It could be fixed/implemented, but I think that means the whole http client building has to be made asynchronous, to read the stream data into a buffer.
Right now, I think the test should be adapted to actually test a working feature.

[CyBot]

I fixed the tests - they now pass the attachment body as a buffer, not a ReadStream.

The test fix should maybe go into a separate commit, I can split them and create a separate PR if requested

[w666]

Hi @CyBot,

Could you allow me to push to your forked repo? I made some changes in the tests.
If no, I will just raise another PR when I merge your PR.

In general, it looks good, seems like it works as expected now.

[w666]

@CyBot I pushed some changes, added additional assertion on server side and uncommented assertions that were disabled some time ago.

[w666]

Approved, I will include this into next release. Thanks for the fix.