Create Registrations API "POST /registrations" 
test
Create API::V1::RegistrationsController
Add POST "/registrations" route
Created 'create' action for 
API::V1::RegistrationsController, tests passing
Update Registrations API "POST /registrations"
test, test passing
Create Registrations API "POST /registrations" 
failure test
Created error render inside 'create' action in
API::V1::RegistrationsController when unsuccessful
Update Registrations API "POST /registrations"
failure test, tests passing
Refactor API::V1::RegistrationsController 
tests and all passing