refactor: repository pattern: rename Save() to Create()

internal/postgres/attendee_repository.go

@@ -76,7 +76,7 @@ func (r *AttendeeRepository) CountForDate(dateID training.DateID) (int, error) {
 	return count, nil
 }
 
-func (r *AttendeeRepository) Save(a *training.Attendee) error {
+func (r *AttendeeRepository) Create(a *training.Attendee) error {
 	_, err := r.db.Exec("INSERT INTO attendee (id, date_id, name, email, company, role, is_student, has_attended, has_paid) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)", a.ID, a.DateID, a.Name, a.Email, a.Company, a.Role, a.IsStudent, a.HasAttended, a.HasPaid)
 	return err
 }