Stripe Tax: Update customer address when needed

Use the billing address entered during checkout to assess the customer's
location for Stripe Tax. This is also needed to avoid an error if an
existing customer lacks an address.

ghost/stripe/lib/StripeAPI.js

@@ -488,6 +488,14 @@ module.exports = class StripeAPI {
             stripeSessionOptions.customer_email = customerEmail;
         }
 
+        // Use the billing address entered during checkout to assess the
+        // customer's location for Stripe Tax. This is also needed to avoid an
+        // error if an existing customer lacks an address. It must not be used
+        // when Stripe does not already have a customer record.
+        if (customer && this._config.enableAutomaticTax) {
+            stripeSessionOptions.customer_update = {address: 'auto'};
+        }
+
         // @ts-ignore
         const session = await this._stripe.checkout.sessions.create(stripeSessionOptions);
 
@@ -537,6 +545,14 @@ module.exports = class StripeAPI {
             }]
         };
 
+        // Use the billing address entered during checkout to assess the
+        // customer's location for Stripe Tax. This is also needed to avoid an
+        // error if an existing customer lacks an address. It must not be used
+        // when Stripe does not already have a customer record.
+        if (customer && this._config.enableAutomaticTax) {
+            stripeSessionOptions.customer_update = {address: 'auto'};
+        }
+
         // @ts-ignore
         const session = await this._stripe.checkout.sessions.create(stripeSessionOptions);
         return session;