Refactored database pkg - added function to detect duplicated rows error

Fixed Register method for detect duplicated username/email

src/internal/service/auth.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 
+	db "git.ego.freeddns.org/egommerce/identity-service/pkg/database"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
@@ -44,6 +45,9 @@ func (a *Auth) Register(email, login, passwd string) (string, error) {
 	sql := `INSERT INTO identity.users(email, username, password) VALUES($1, $2, $3) LIMIT 1 RETURNING id`
 	err := a.db.QueryRow(context.Background(), sql, email, login, passwd).Scan(&id)
 	if err != nil {
+		if err = db.IsDuplicatedRow(err); err != nil {
+			return "", errors.New("username/email is already taken")
+		}
 		return "", errors.New("Failed to create new user: " + err.Error())
 	}