Rate limits application of coupon codes by user ID to prevent
brute forcing. Refactors the rate limiter to allow limiting based
on arbitrary criteria and not just by IP.
Change-Id: I99d6749bd5b5e47d7e1aeb0314e363a8e7259dba
Error message for attempting to activate an already-activated
account is removed from its own page and incorporated into the
login page in an identical manner to the message that appears
upon successful activation.
Change-Id: I29cd2685a7808fa71d34a439c86a38eb5fc3e199