computedID in idpv3

[Cantor, Scott]

> Together a + b are strong indicators (or so I would claim) that most
> existing SSP deployments will not be prepared to handle IDPs' change
> from Attribute to Subject without (small) code/config changes.
> That's certainly not ideal but it's also a far cry from calling the
> implementation broken.

Others have used the word so I did, but correction noted, likely not for the first time. That said, code changes essentially become the immovable object in my experience, no matter how small they are.

-- Scott