Use RSpec's let feature.  Ban deprecated should matching.
Standardize on usage of 'path' and 'uri'

A path is the path to the resource while a uri is composed of a path
and any additional query parameters.  These definitions are no doubt
incorrect according to various RFCs, but they are what I'm going with.
Allow clients to pin themselves to a UUID.
Add guest id deletion.
Make status code matchers a more succinct.
Add user CRUD methods.