fix: /logout routes; improved error handling for invites

internal/domain/registration.go

@@ -3,6 +3,7 @@ package domain
 import (
 	"context"
 	"log/slog"
+	"time"
 )
 
 type RegistrationService struct {
@@ -22,6 +23,13 @@ func (s *RegistrationService) Register(ctx context.Context, inviteCode string, e
 		return nil, err
 	}
 
+	if invite.ConsumedAt != nil {
+		return nil, ErrInviteConsumed
+	}
+	if invite.ExpiresAt.Before(time.Now()) {
+		return nil, ErrInviteExpired
+	}
+
 	var user *User
 	err = s.tx.WithinTx(ctx, func(ctx context.Context) error {
 		user, err = s.UserService.CreateUser(ctx, email, username, password)