FAL2 - Assertion Presentation

[deansaxe]

"Assertions MAY also be proxied to facilitate federation between IdPs and RPs using different presentation methods, as discussed in detail in Sec. 3.2.3."

We have not discussed proxied federation and its suitability in IPSIE deployments. Queuing this up for discussion.

[deansaxe]

@Tedyber has agreed to write guidance for IdP chaining in #97. IdP chaining looks and acts similarly to a proxy, therefore I sugggest that this issue is reviewed alongside #97 and closed if consensus is the work on #97 sufficiently addresses the language in SP800-63C rev4.