Add setting to globally disable asking for a copy of answers

There is a setting on the form to configure whether or not the user is
asked if they want to ask for a copy of their answers by logging in
with One Login.

Add a global setting to allow us to disable this feature for all forms
in the case that One Login is unavailable.

Author: stephencdaly

app/models/form.rb

@@ -65,6 +65,7 @@ def welsh?
   end
 
   def copy_of_answers_enabled?
+    return false unless Settings.copy_of_answers_enabled
     return false unless form_document.respond_to?(:send_copy_of_answers)
 
     form_document.send_copy_of_answers == "enabled"

config/settings.yml

@@ -74,3 +74,6 @@ show_browser_during_tests: false
 cloudwatch_metrics_enabled: false
 
 analytics_enabled: false
+
+# Allows us to globally disable users getting a copy of their answers in the case that One Login is unavailable.
+copy_of_answers_enabled: true

spec/models/form_spec.rb

@@ -186,6 +186,16 @@
       it "returns true" do
         expect(form.copy_of_answers_enabled?).to be true
       end
+
+      context "when the global copy_of_answers_enabled setting is set to false" do
+        before do
+          allow(Settings).to receive(:copy_of_answers_enabled).and_return(false)
+        end
+
+        it "returns false" do
+          expect(form.copy_of_answers_enabled?).to be false
+        end
+      end
     end
 
     context "when send_copy_of_answers is \"disabled\"" do