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
Also moved to default crawl delay bing so no more than a req every 5 seconds is allowed
New site settings:
"slow_down_crawler_user_agents" - list of crawlers that will be slowed down
"slow_down_crawler_rate" - how many seconds to wait between requests
Not enforced server side yet
