enable using different policies for different services

[vlmutolo]

This is already possible by creating an entirely separate BiscuitAuth object per service. The issue is that this makes updating each of the individual auth objects difficult. But maybe we could implement some kind of aggregate auth object like HashMap<Name, BiscuitAuth> that would be able to update the various policies by name with a user-defined update mechanism. That would make this pattern a lot more ergonomic.