Appends the given entry to the request. This can be a simple key/value pair of strings or file uploads.
Gets the content type header that should be set in the request. This includes the type and boundary that is applicable to the toBytes method.
Deletes any entries from the set with the given key.
Returns all the current entries in the object.
Returns the first entry with the given key, or MimePart.init if there is nothing.
Returns the all entries with the given key.
Returns true if the given key exists in the set.
Sets the given key to the given value if it exists, or appends it if it doesn't.
Returns bytes applicable for the body of this request. Use the contentType method to get the appropriate content type header with the right boundary.
Creates a multipart/form-data object that is suitable for file uploads and other kinds of POST.
It has a set of names and values of mime components. Names can be repeated. They will be presented in the same order in which you add them. You will mostly want to use the append method.
You can pass this directly to HttpClient.request.
Based on: https://developer.mozilla.org/en-US/docs/Web/API/FormData