Add more catches for stripe events

app/stripe_webhook.rb

@@ -11,5 +11,33 @@ post '/stripe_webhook' do
       body:    "#{username}\n#{email}\n#{Site[username: username].uri}"
     })
   end
+
+  if event['type'] == 'charge.failed'
+    site_id = event['data']['object']['description'].split(' - ').last
+    site = Site[site_id]
+
+    EmailWorker.perform_async({
+      from:    'web@neocities.org',
+      to:      site.email,
+      subject: "[Neocities] There was an issue charging your card",
+      body:    Tilt.new('./views/templates/email/charge_failure.erb', pretty: true).render(self)
+    })
+  end
+
+  if event['type'] == 'customer.subscription.deleted'
+    site_id = event['data']['object']['description'].split(' - ').last
+    site = Site[site_id]
+    site.stripe_subscription_id = nil
+    site.plan_type = nil
+    site.save_changes validate: false
+
+    EmailWorker.perform_async({
+      from:    'web@neocities.org',
+      to:      site.email,
+      subject: "[Neocities] Supporter plan has ended",
+      body:    Tilt.new('./views/templates/email/supporter_ended.erb', pretty: true).render(self)
+    })
+  end
+
   'ok'
 end

views/templates/email/charge_failure.erb

@@ -0,0 +1,10 @@
+Hello,
+
+We're writing to let you know that Neocities has had an issue charging your card. We will try again automatically in a few days, but we just wanted to give you a heads up in case something is wrong with your card.
+
+We will retry over the next few weeks. If we can't make a successful charge, your account will be downgraded from supporter to the free plan.
+
+If you need to change the card on file, you can do so on the settings page. If you run into any issues, please contact us at https://neocities.org/contact.
+
+Regards,
+- The Neocities Team

views/templates/email/supporter_ended.erb

@@ -0,0 +1,11 @@
+Hi there,
+
+We're just emailing to let you know that your supporter plan has ended.
+
+If you feel this is in error, please re-register for a supporter account on Neocities, or contact us at https://neocities.org/contact and we'll take a look.
+
+We're sorry to see you go, but we understand. Thanks for helping us out (it means a lot), and our best wishes to you!
+
+Regards,
+
+- The Neocities Team