User Registration

## User Registration endpoint exists in API template

### Acceptance Criteria
1. Can send email, password as jSON payload to endpoint.
1. On successful API call, an email item is created to be sent to the user to verify their registration.
 - Token is sent from `user_tokens` table.
 - Email does not yet auto-send because workers are not set up yet.
1. `verified` flag exists in `users` table; set to 0 until the user verifies their registration.