title: how to add trial period in Checkout session in Stripe
body: <p>I have this code:</p>
  <pre><code>const session = await stripe.checkout.sessions.create({
      billing_address_collection: 'auto',
      payment_method_types: ['card'],
      customer_email: email,
      line_items: [
          {
          price: priceID,
          // For metered billing, do not pass quantity
          quantity: 1,
          },
      ],
      // subscription_data: 
      mode: 'subscription',
      success_url: `${YOUR_DOMAIN}/gen_trainerclientlist`,
      cancel_url: `${YOUR_DOMAIN}/cancel.html`,
      });
  </code></pre>
  <p>and I want to add this:</p>
  <pre><code>    subscription_data: {
         trial_end=1605387163
      }
  </code></pre>
  <p>but whereever I put it, it doesn't work! How do i fix this?</p>