Read Object POST Parameters from Form Fields

[lscspirit]

According to AWS S3 documentation, in a POST object request, parameters are passed through the multipart form instead of as HTTP headers (see http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html). This change makes Fake S3 parse and use parameters from the multipart form in the case of a object POST request.

This change is needed to properly handle a presigned object POST request. At the moment, FakeS3 would create an object under the wrong content type multipart/form-data because that's what the 'Content-Type' header said in the HTTP POST request; yet, the correct content type is passed along as one of the multipart form field of the request.

[summera]

@lscspirit @jubos I had an issue with Content-Type when using fake-s3 with multipart uploads because my server validates Content-Type. This fixed my issue. 👍

[lscspirit]

Any chance of getting this pull request merged?

[rposborne]

@jubos What are your thoughts on this? Would love to see this in master.