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
Vinoth Kannan
Vinoth Kannan
Sam Saffron
Penar Musaraj
Gerhard Schlager
Régis Hanol