ignores case when enforcing unique emails for users

You should be able to check for existing violations in your db like this:

  User.all.map { |u| u.email }
      .reduce(Hash.new(0)) { |a,b| a[b.downcase] += 1; a }
      .select { |k,v| v > 1 }
adds more database indexes
adds data scrubbing tasks to get rid of personal data in old conferences