Allow determination of mandatory or optional fields

[simonaszilinskas]

Description

Currently, all fields in the registration form are mandatory. To provide more flexibility, we should allow administrators to specify whether a field is mandatory or optional.

Proposed Solution:

1. Add a config from the admin panel that allows for every field to configure it's optionality
2. Update the form validation logic to enforce the mandatory or optional requirement for each field.
3. Modify the form rendering to visually distinguish mandatory and optional fields for better user experience (if needed I can make some mockups)