New User Creation Flow with Pre-Generated UUID

[#79720994] https://www.pivotaltracker.com/story/show/79720994

Signed-off-by: Rob Szumlakowski <rszumlakowski@pivotal.io>
Consume extra information about existing user in case of conflict when creating a user

[#79720994] https://www.pivotaltracker.com/story/show/79720994

Signed-off-by: Madhura Bhave <mbhave@gopivotal.com>