Previously, rate limits had to apply to a particular user or a
particular IP address, or both. This adds support for global
rate-limits, where the limit will apply to everyone trying to perform
the action. This probably won't be used much overall, but might be
necessary for certain cases where something abusive is happening and it
can't be easily blocked by user or IP.
This is a bit ugly and would probably be better implemented by having a
separate class that inherits from RateLimitedAction or something
similar, but it will do the job.
Deimos