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 exposes the token in the Sidekiq dashboard which can be
viewed by an admin and defeats the purpose of using a token
in the download backup email ink.