Added apple gamekit auth

Untested rn

src/Adapters/Auth/apple.js

@@ -0,0 +1,52 @@
+var Parse = require('parse/node').Parse;
+const { URL } = require('url');
+var jwt = require('jsonwebtoken');
+var jwksClient = require('jwks-rsa');
+var verifier = require('gamecenter-identity-verifier');
+
+// Returns a promise that fulfills iff this nsa id token is valid
+function validateAuthData(authData, authOptions) {
+    console.log("going to validate for apple");
+    console.log(authData);
+    var necessaries = ["timestamp", "salt", "id", "bundleId", "signature", "publicKeyUrl"];
+    for (var necessary in necessaries) {
+        if (!(necessary in authData)) {
+            error("Auth data does not have property " + necessary);
+        }
+    }
+
+    var identity = {
+        publicKeyUrl: authData["publicKeyUrl"],
+        timestamp: authData["timestamp"],
+        signature: authData["signature"],
+        salt: authData["salt"],
+        playerId: authData["id"],
+        bundleId: authData["bundleId"]
+    };
+
+    return new Promise(function(resolve, reject) {
+        verifier.verify(identity, function (err, token) {
+            if (!err) {
+                resolve(token);
+            }
+            else {
+                reject("Error authenticating with gamekit: " + err.message);
+            }
+        });
+    });
+        
+}
+
+// we're validating the bundleId in the in the user auth method
+function validateAppId() {
+  return Promise.resolve();
+}
+
+function error(message) {
+    throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND, message);
+}
+
+module.exports = {
+  validateAppId,
+  validateAuthData
+};

src/Adapters/Auth/index.js

@@ -18,6 +18,7 @@ const wechat = require("./wechat");
 const weibo = require("./weibo");
 const steam = require("./steam");
 const nintendo = require("./nintendo");
+const apple = require("./apple");
 
 const anonymous = {
   validateAuthData: () => {
@@ -47,7 +48,8 @@ const providers = {
   wechat,
   weibo,
   steam,
-  nintendo
+  nintendo,
+  apple
 }
 function authDataValidator(adapter, appIds, options) {
   return function(authData) {