RequestedAttributes and EntityAttributes

[Brent Putman]

> We may want to optimize that by extending the SAMLMetadataContext to carry
> the effective ACS entry,


Just a minor suggestion: To keep things clean, I would suggest maybe
create a new context to carry metadata info that is specific to IdP-side
use cases, and hang that underneath the SAMLMetadataContext. Or
something like that.  The SAMLMetadataContext was intended to be more
generic and isn't specific to an IdP or SP use case.