Attributes and Predicates

[Rod Widdowson]

Answering myself in one case:

> The only counter example I might see is that the actual mechanism to
locate
> (for instance) the RP identity might be different when resolving
attributes
> to when encoding them.  

I had forgotten that we had move things so that *is* the case in the
attribute resolution case the principal is right there in the
ResolutionContext.

So my question now is, give that :

> we cannot detect at configuration time if someone has plugged a
> Predicate<AttributeResolverContext> in to somewhere which expects a
> Predicate<ProfileRequestContext> - you'll just get an ugly run time class
> cast exception.  

Do we want to put in any blade guards to stop people injecting the wrong
sort of Predicate?