Logging the value of the id attribute of the <saml2p:Response> element

[Cantor, Scott]

https://wiki.shibboleth.net/confluence/display/IDP4/AuditLoggingConfiguration

Lower case "I" is the assertion ID.

Capital "I" is the inbound message ID.

Two capitals ("II") is the InResponseTo value.

Three capitals ("III") is the outbound message ID.

-- Scott