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Signup feature with validations. -John & Gordon
@robwagner33 - As per your concern about having a "a user exists" api call. The reason this was created was for AJAX checking client side when a user is entering in an email or username. 
I think pre-validating client side makes for a better user experience and thus needs an API call (unless I am missing something?).  But if you would prefer to do all the check server side on a post submit and return with errors thats fine too, just let me know your preference.