You’ll probably hate me for saying this, but have you thought about just using an Action Button?
You could have a button for Candidates (called “Hired!”) which when pressed, will create a User and transfers the necessary info from the Candidate (name, email address, phone # etc.).
The button could also trigger other things (like assigning the person to training, or arranging that they get sent a welcome bunch of flowers, or whatever 
)
You can also use the button to add the relationship between the Candidate entity and the User entity so that you can always look back at what info was recorded during the recruitment process.
Similarly, you might want a button (called “Didn’t make it”) which ensures that sensitive information on candidates who didn’t join the team gets deleted (for GDPR compliance or whatever) or maybe adds a time stamp so that these things can become flagged as due after a pre-determined period of time.
FWIW, I have an Employee type that isn’t the same as the User type, since some employees might never end up using Fibery, but I still want to be able to record various details related to employment.
i.e. all Users are Employees, but not all Employees are Users