Add support for MultipartFormData to the Play Scala WS library

MultipartFormDataWriteable.scala

package utilities

import java.io.{ByteArrayOutputStream, File}

import com.ning.http.client.FluentCaseInsensitiveStringsMap
import com.ning.http.multipart.{MultipartRequestEntity, FilePart, StringPart}
import play.api.http.HeaderNames._
import play.api.http.{ContentTypeOf, Writeable}
import play.api.mvc.{Codec, MultipartFormData}

object MultipartFormDataWriteable {

    implicit def contentTypeOf_MultipartFormData[A](implicit codec: Codec): ContentTypeOf[MultipartFormData[A]] = {
        ContentTypeOf[MultipartFormData[A]](Some("multipart/form-data; boundary=__X_PROCESS_STREET_BOUNDARY__"))
    }

    implicit def writeableOf_MultipartFormData(implicit contentType: ContentTypeOf[MultipartFormData[File]]): Writeable[MultipartFormData[File]] = {
        Writeable[MultipartFormData[File]]((formData: MultipartFormData[File]) => {

            val stringParts = formData.dataParts flatMap {
                case (key, values) => values map (new StringPart(key, _))
            }

            val fileParts = formData.files map { filePart =>
                new FilePart(filePart.key, filePart.ref, filePart.contentType getOrElse "application/octet-stream", null)
            }

            val parts = stringParts ++ fileParts

            val headers = new FluentCaseInsensitiveStringsMap().add(CONTENT_TYPE, contentType.mimeType.get)
            val entity = new MultipartRequestEntity(parts.toArray, headers)
            val outputStream = new ByteArrayOutputStream
            entity.writeRequest(outputStream)

            outputStream.toByteArray

        })(contentType)
    }

}