This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
This makes more sense than having the guardian take an accessor.
The logic belongs in the Serializer, where the JSON is calculated.
Also removed some of the DRYness in the spec. It's fewer lines
and made it easier to test the option on the serializer.
Sam Saffron
Daniel Waterworth
Guo Xiang Tan
Gerhard Schlager
Robin Ward
Maja Komel
Leo McArdle