Refactor all auth adapters to reduce duplications (#4954)

* Refactor all auth adapters to reduce duplications

* Adds mocking and proper testing for all auth adapters

* Proper testing of the google auth adapter

* noit

src/Adapters/Auth/spotify.js

@@ -1,5 +1,5 @@
 // Helper functions for accessing the Spotify API.
-var https = require('https');
+const httpsRequest = require('./httpsRequest');
 var Parse = require('parse/node').Parse;
 
 // Returns a promise that fulfills iff this user id is valid.
@@ -36,29 +36,12 @@ function validateAppId(appIds, authData) {
 
 // A promisey wrapper for Spotify API requests.
 function request(path, access_token) {
-  return new Promise(function(resolve, reject) {
-    https.get({
-      host: 'api.spotify.com',
-      path: '/v1/' + path,
-      headers: {
-        'Authorization': 'Bearer ' + access_token
-      }
-    }, function(res) {
-      var data = '';
-      res.on('data', function(chunk) {
-        data += chunk;
-      });
-      res.on('end', function() {
-        try {
-          data = JSON.parse(data);
-        } catch(e) {
-          return reject(e);
-        }
-        resolve(data);
-      });
-    }).on('error', function() {
-      reject('Failed to validate this access token with Spotify.');
-    });
+  return httpsRequest.get({
+    host: 'api.spotify.com',
+    path: '/v1/' + path,
+    headers: {
+      'Authorization': 'Bearer ' + access_token
+    }
   });
 }