Returns a specification to start this module under a supervisor.

See Supervisor.

@spec get(GenServer.server(), String.t()) :: :ok

Download and install the firmware at the specified URL

@spec start_link(pid()) :: GenServer.on_start()

Start the downloader process

A callback process should be passed

Messages will be received in the shape:

• {:fwup_message, message} - see the docs for Fwup for more info.
• {:http_error, {status_code, body}}
• {:http_error, :timeout}
• {:http_error, :too_many_redirects}

@spec stop(GenServer.server()) :: :ok

Stop the downloader