:encoding - sets encoding for the incoming form fields. Defaults to utf8.
:max-fields-size - Limits the amount of memory all fields (not files) can allocate in bytes. If this value is exceeded, an error event is emitted. The default size is 2MB.
:max-fields - Limits the number of fields that will be parsed before emitting an error event. A file counts as a field in this case. Defaults to 1000.
:max-files-size - Only relevant when autoFiles is true. Limits the total bytes accepted for all files combined. If this value is exceeded, an error event is emitted. The default is Infinity.
:upload-dir - Only relevant when autoFiles is true. The directory for placing file uploads in. Defaults to (.tmpDir os).
:progress-fn - function that will be called when bytes are received, should expect two fields: bytes-eeceived, bytes-expected