How We Let Users Register with Just a Phone Number on a NOT NULL Email Column

When integrating a shop frontend with an ERP system sharing a user table with a NOT NULL + UNIQUE email column, the team needed to allow phone-only registration for wholesale buyers. Instead of migrating the database schema to make email nullable, they generated placeholder emails (shop_{phone}@shop.local) on the backend when no email was provided, satisfying the constraint while keeping registration simple.