Metadata on subscriptions not working.

      const { error: upgradeError } = await authClient.subscription.upgrade({
        plan,
        successUrl,
        cancelUrl,
        annual: isAnnual,
        metadata: {
          ga_client_id: clientId,
        },
        fetchOptions: {
          headers: {
            'x-currency': currency,
            // Pass GA client_id for server-side GTM attribution
            ...(clientId && { 'x-ga-client-id': clientId }),
          },
        },
      });

      const { error: upgradeError } = await authClient.subscription.upgrade({
        plan,
        successUrl,
        cancelUrl,
        annual: isAnnual,
        metadata: {
          ga_client_id: clientId,
        },
        fetchOptions: {
          headers: {
            'x-currency': currency,
            // Pass GA client_id for server-side GTM attribution
            ...(clientId && { 'x-ga-client-id': clientId }),
          },
        },
      });