Using phoenix_live_view_dropzone component

Can someone help me with using phoenix_live_view_dropzone component.
I managed to start the upload, responding to phx-dropzone event

case event do
“generate-url” ->
file_data = %{id: payload[“id”], url: “/api/uploads”}

but the upload controller always receives empty payload

def update(conn, upload) do
upload |> IO.inspect # this shows {}