Context navigation in the Abstract Profile Actions.

[Rod Widdowson]

This is mostly for Scott I guess...

I am about to start moving things over from the old
"AttributeRecipientContext" to the AttributeFilterContext and the
AttributeResolutionContext (as discussed late last year).

I'm starting with the Principal which it appears I need to get from the
SubjectContext.

It looks like the paradigm is to:

1) In the constructor assume the subject context will normally be a child of
the ProfileContext and to set up a default Function<ProfileRequestContext,
SubjectContext> which does that.

2) To allow this to be overridden with a setter.

3) In the preExecute stage populate a private field with the subject context
located with the function we set up above.

4) In the execute stage use it (by putting the name into the
AttributeContext which is generated).

Before I start on this I just wanted to check that that would be the
expected code..

I suspect that next I will have questions about where to find the other
Strings (attributeIssuerID, attributeRecipientID,
principalAuthenticationMethod), but I'll do more code reading before I ask
that...

Thanks

Rod