Brief
Instead of staff this entity should just be called person. We will store not just workers here.
Every user should have one optional person filed in an one-to-one relation with his account.
Will add an uneditable field called Display name to the user which value is dependent on the following rules:
- if no person is assigned then the Display name = Login
- if person is selected then the Display name = First and Last name
In all reports and entities we should always show the display name.
The user entity should only be used as credentials.
Only admins should be able to change the person related to an User.
Fileds: first name, last name, description; should be only in the person entity.