Connect social accounts issue

[tezavrat]

Steps to reproduce:
1. User signin in to first account and presses to connect to Facebook
2. User signin in to second account and presses to connect to the same Facebook account
3. User signin by facebook
4. User receives error "Your sign in information was incorrect. Please try again or sign up"

Reason: every time you connect the same Facebook account system creates new record in "UserConnection" table. The difference is only "userId" column

Proposal: every time you connect the same Facebook account prompt to user a message "This Facebook account is already connected. Do you want to reconnect it ?". After confirmation update userId field.

Also it would be nice to have unique key (providerId, providerUserId) in "UserConnection" table. I already posted it :
http://forum.springsource.org/showth...epository.sql)