Adding attributes in intercept flow

[Daniel Lutz]

We consider implementing an intercept flow that adds another attribute
to the existing set of attributes (i.e. after the regular attribute resolution
took place). The source values for this attribute aren't known before the execution
of this intercept flow.

As far as I know, the IdP's regular attribute resolution stores the resolved attributes
to the context "ProfileRequestContext -> RelyingPartyContext -> AttributeContext".

Is the context "ProfileRequestContext -> RelyingPartyContext -> AttributeContext"
considered part of the API? Can we safely add attributes there?

I'm aware that we would need to take care of filtering ourselves.

(BTW, this relates to Etienne's thread "Building a composite attribute from sets of attributes".)

  Daniel