Minor Description
The model for Address doesn't support setting both the address and the id. And, since it doesn't support setting the href it doesn't allow accessing an address specifically by id (which is how you would do it in OpenStack).
Even just making the "to_hash" method on Address use a ternary on href and making that attribute settable would be an acceptable solution. The only real use case is to be able to retrieve address details for an individual address.
An example from mock driver:
<address href="http://localhost:3001/api/addresses/192.168.0.4" id="192.168.0.4"><ip>192.168.0.4</ip><actions><link href="http://localhost:3001/api/addresses/192.168.0.4" method="delete" rel="destroy"/><link href="http://localhost:3001/api/addresses/192.168.0.4/associate" method="post" rel="associate"/></actions></address>
But 192.168.0.4 isn't an id, it's an IP