Cookie settings use single consent API

- updates the JavaScript for the cookie settings page to use the single consent API code
- stores an internal variable to check whether or not to use the consent API
- if false, behaviour should be as normal
- if true, should yield setting of consent cookies entirely to the consent API code
- note that this code sends its own callback function for the consent API, which sets the initial form values on page load, this means that any delay in the API call will result in these fields being unfilled until it responds

app/assets/javascripts/govuk_publishing_components/lib/cookie-settings.js

@@ -12,12 +12,19 @@ window.GOVUK.Modules = window.GOVUK.Modules || {};
     document.querySelector('form[data-module=cookie-settings]')
       .addEventListener('submit', this.$module.submitSettingsForm)
 
-    this.setInitialFormValues()
+    this.$module.useConsentApi = window.GOVUK.singleConsent.useConsentApi()
+    if (this.$module.useConsentApi) {
+      window.GOVUK.singleConsent.init(this.setInitialFormValues())
+    } else {
+      this.setInitialFormValues()
+    }
   }
 
   CookieSettings.prototype.setInitialFormValues = function () {
     if (!window.GOVUK.cookie('cookies_policy')) {
-      window.GOVUK.setDefaultConsentCookie()
+      if (!this.$module.useConsentApi) {
+        window.GOVUK.setDefaultConsentCookie()
+      }
     }
 
     var currentConsentCookie = window.GOVUK.cookie('cookies_policy')
@@ -57,13 +64,15 @@ window.GOVUK.Modules = window.GOVUK.Modules || {};
       }
     }
 
-    window.GOVUK.setConsentCookie(options)
-    window.GOVUK.setCookie('cookies_preferences_set', true, { days: 365 })
+    if (this.$module.useConsentApi) {
+      window.GOVUK.singleConsent.setPreferences(null, options)
+    } else {
+      window.GOVUK.setConsentCookie(options)
+      window.GOVUK.setCookie('cookies_preferences_set', true, { days: 365 })
+    }
 
     this.fireAnalyticsEvent(options)
-
     this.showConfirmationMessage()
-
     return false
   }