ID5 userId submodule (prebid#3798)

* Extract GDPRApplies in userId.js to make it available to cookie-sync requiring it

* Adding id5 userId submodule, tests and documentation

* Fixed typo in test name for unifiedid

* Adding test to userId for ID5

* Follow correct naming convention for GDPRApplies: renamed to isGDPRApplicable

* Refactoring of id5 module following refactoring of userId module.

* Moved init of id5 user module at the end of the id5 module itself

* regroup import to avoid a CircleCI Bug

modules/userId/index.js

@@ -160,13 +160,22 @@ function getStoredValue(storage) {
   return storedValue;
 }
 
+/**
+ * test if consent module is present, and if GDPR applies
+ * @param {ConsentData} consentData
+ * @returns {boolean}
+ */
+export function isGDPRApplicable(consentData) {
+  return consentData && typeof consentData.gdprApplies === 'boolean' && consentData.gdprApplies;
+}
+
 /**
  * test if consent module is present, applies, and is valid for local storage or cookies (purpose 1)
  * @param {ConsentData} consentData
  * @returns {boolean}
  */
-function hasGDPRConsent(consentData) {
-  if (consentData && typeof consentData.gdprApplies === 'boolean' && consentData.gdprApplies) {
+export function hasGDPRConsent(consentData) {
+  if (isGDPRApplicable(consentData)) {
     if (!consentData.consentString) {
       return false;
     }