This should make the importer more resilient to incomplete or damaged
backups. It will disable some validations and attempt to automatically
repair category permissions before importing.
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
