let
    Web.MultiPartPost = (url as text, parts as record) as binary =>
        let
            unique = Text.NewGuid(),
            boundary = "--" & unique,
            crlf = "#(cr)#(lf)",
            item = (name, value) =>
                let
                    filename = Value.Metadata(value)[name]?,
                    contentType = Value.Metadata(value)[type]?,
                    line1 = "Content-Disposition: form-data; name=""" & name & """" &
                        (if filename = null then "" else "; filename=""" & filename & """"),
                    line2 = if contentType = null then {} else { "Content-Type: " & contentType },
                    lines = { boundary, line1 } & line2 & { "", value }
                in
                    Text.Combine(lines, crlf) & crlf,
            body = Text.Combine(List.Transform(Record.FieldNames(parts), each item(_, Record.Field(parts, _)))) & boundary & "--" & crlf
        in
            Web.Contents(url, [
                Headers=[#"Content-Type"="multipart/form-data; boundary=" & unique],
                Content=Text.ToBinary(body)
            ]),
    fileContents =
"{""code"": ""15315""}
{""code"": ""526133""}
{""code"": ""43011""}
{""code"": ""83988""}
{""code"": ""182347""}",
    parts = [
        id = "c9c43e63-9372-441c-9ab7-c5e66d7da371",
        file = fileContents meta [name="upload.txt", type="text/plain"],
        locale = "en-US"
    ],
    Result = Web.MultiPartPost("http://foo.com/bar/baz", parts)
in
    Result