Fix Stripe tax ID collection error on course checkout

The course.checkout route enables tax_id_collection on a Cashier checkout
for a user who already has a Stripe customer. Stripe requires
customer_update[address]=auto so it can write the collected billing
address back to the existing customer for tax ID validation. Cashier
only auto-fills customer_update[name], so Stripe rejected the request.

Add customer_update => [name, address] => auto, matching the cart,
license renewal, and mobile pricing checkout flows, and assert it in the
course checkout test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: simonhamp

routes/web.php

@@ -153,6 +153,10 @@
         'metadata' => $metadata,
         'allow_promotion_codes' => true,
         'billing_address_collection' => 'required',
+        'customer_update' => [
+            'name' => 'auto',
+            'address' => 'auto',
+        ],
         'tax_id_collection' => ['enabled' => true],
         'invoice_creation' => [
             'enabled' => true,

tests/Feature/CoursePageTest.php

@@ -127,6 +127,10 @@ public function retrieve(): Customer
         $this->assertStringContainsString(route('cart.success'), $capturedParams['success_url']);
         $this->assertStringContainsString('{CHECKOUT_SESSION_ID}', $capturedParams['success_url']);
 
+        $this->assertTrue($capturedParams['tax_id_collection']['enabled']);
+        $this->assertSame('auto', $capturedParams['customer_update']['address'] ?? null, 'Tax ID collection requires customer_update[address] = auto for existing customers');
+        $this->assertSame('auto', $capturedParams['customer_update']['name'] ?? null);
+
         Carbon::setTestNow();
     }