Send an email when the invoice is failed to charge

We automate the process of sending emails when an invoice fails to
charge, including error details from the Stripe API.

We also add the support email as a CC, allowing the entire team to
follow up with the customer if needed.

model/invoice.rb

@@ -79,6 +79,7 @@ def charge
     end
 
     Clog.emit("Invoice couldn't charged with any payment method.") { {invoice_not_charged: {ubid: ubid}} }
+    send_failure_email(errors)
     false
   end
 
@@ -97,6 +98,21 @@ def send_success_email(below_threshold: false)
       button_title: "View Invoice",
       button_link: "#{Config.base_url}#{project.path}/billing#{ser[:path]}")
   end
+
+  def send_failure_email(errors)
+    ser = Serializers::Web::Invoice.new(:detailed).serialize(self)
+    Util.send_email(ser[:billing_email], "Urgent: Action Required to Prevent Service Disruption",
+      cc: Config.mail_from,
+      greeting: "Dear #{ser[:billing_name]},",
+      body: ["We hope this message finds you well.",
+        "We've noticed that your credit card on file has been declined with the following errors:",
+        *errors.map { "- #{_1}" },
+        "The invoice amount of #{ser[:total]} tried be debited from your credit card on file.",
+        "To prevent service disruption, please update your payment information within the next two days.",
+        "If you have any questions, please send us a support request via support@ubicloud.com."],
+      button_title: "Update Payment Method",
+      button_link: "#{Config.base_url}#{project.path}/billing")
+  end
 end
 
 Invoice.unrestrict_primary_key

spec/model/invoice_spec.rb

@@ -60,6 +60,7 @@
       expect(Clog).to receive(:emit).with("Invoice couldn't charged.").and_call_original.twice
       expect(Clog).to receive(:emit).with("Invoice couldn't charged with any payment method.").and_call_original
       expect(invoice.charge).to be false
+      expect(Mail::TestMailer.deliveries.length).to eq 1
     end
 
     it "can charge from a correct payment method even some of them are not working" do