The `ipaddr` arg here is being interpreted as a positional arg (since
the keyword arg doesn't exist), which results in an invalid connection
object. This was causing push notifications to silently fail.
We should initialise the property on the object instead.
We are not trying to handle user input so `cast` can be a no-op. Also
extract the base36 normalization logic, let the binary class handle the
serialize encoding and add some tests.
Kevin McConnell