feat(API): optional display name on users

internal/infrastructure/useCases/UpdateUserProfile.go

@@ -0,0 +1,25 @@
+package useCases
+
+import (
+	"RenewCMS/internal/domain/user"
+	"strings"
+	"unicode/utf8"
+)
+
+const maxDisplayNameRunes = 60
+
+type UpdateUserProfileUseCase struct {
+	userRepository user.Repository
+}
+
+func NewUpdateUserProfileUseCase(userRepository user.Repository) *UpdateUserProfileUseCase {
+	return &UpdateUserProfileUseCase{userRepository}
+}
+
+func (u *UpdateUserProfileUseCase) UpdateDisplayName(userId uint32, displayName string) (user.User, error) {
+	trimmed := strings.TrimSpace(displayName)
+	if utf8.RuneCountInString(trimmed) > maxDisplayNameRunes {
+		return user.User{}, user.ErrInvalidDisplayName
+	}
+	return u.userRepository.UpdateDisplayName(userId, trimmed)
+}