Include date of enrollment for oxExternalUid

[jgomer2001]

can we send along the date of enrollment in the metadata? otherwise we’re not able to give the date added in oxTrust.. should also be displayed in Casa its a helpful piece of data

This affects passport_social, passport_saml, and casa account linking plugin

Changes should not disturb otp/hotp since that will require modifications in otp script, otp casa script, and casa itself (enrollment timestamps for otp are already stored elsewhere).

[jgomer2001]

I'm moving this to 5.0, so far havent' heard of someone in need of this feature