Convenience method for multipart/form-data requests

[dondi]

This is motivated by and based on #190

Hope you don’t mind the warts and all (particularly the missing unit tests) @pcantrell —I’m very much a newbie in iOS dev, but I tried to not let that discourage me and sort of took your invitation from that issue thread at its word 😬

This same code is currently quite functional in an iOS app I’m working on that uploads files to an Amazon S3 bucket by way of a signed S3 URL. A sample call looks like this:

service.resource(absoluteURL: "http://some.multipart-server.com/asset).request(.post,
        multipart: ["key": "12345", "token": "abcde"]
        files: ["file": Resource.FilePart(filename: "image.jpg", type: "image/jpeg", data: data)],
        order: ["token", "key", "file"] // If server requires `token` to come before `key`
    ).onSuccess { entity in
        uploadCallback(entity)
    }.onFailure { error in
        fail(error)
    }

Shoutout and thanks to @Alex293 whose code in the issue thread is still pretty much what this convenience method is.

I’m happy to start the conversation of getting this convenience helper in to Siesta. Thanks!

[pcantrell]

Thanks for this PR, dondi, and sorry for letting it languish! I love the idea. I’ll give it a design review for the next minor release of Siesta.

[dondi]

No worries @pcantrell! I know how it goes 🙂 Glad you like the idea and I’ll just monitor the PR as things develop.

[romansavrulin]

Hello! Any chance to see it merged?