Auth Adapters refactoring (#3177)

* Moves all authentication providers to Adapter/Auth

* refactors specs

* Deprecates oauth option in favor of auth option

- Deprecates facebookAppIds option (in favor of auth.facebook.appIds)
- Adds warnings about the deprecated options

* nits

src/Adapters/Auth/github.js

@@ -0,0 +1,51 @@
+// Helper functions for accessing the github API.
+var https = require('https');
+var Parse = require('parse/node').Parse;
+
+// Returns a promise that fulfills iff this user id is valid.
+function validateAuthData(authData) {
+  return request('user', authData.access_token)
+    .then((data) => {
+      if (data && data.id == authData.id) {
+        return;
+      }
+      throw new Parse.Error(
+        Parse.Error.OBJECT_NOT_FOUND,
+        'Github auth is invalid for this user.');
+    });
+}
+
+// Returns a promise that fulfills iff this app id is valid.
+function validateAppId() {
+  return Promise.resolve();
+}
+
+// A promisey wrapper for api requests
+function request(path, access_token) {
+  return new Promise(function(resolve, reject) {
+    https.get({
+      host: 'api.github.com',
+      path: '/' + path,
+      headers: {
+        'Authorization': 'bearer '+access_token,
+        'User-Agent': 'parse-server'
+      }
+    }, function(res) {
+      var data = '';
+      res.on('data', function(chunk) {
+        data += chunk;
+      });
+      res.on('end', function() {
+        data = JSON.parse(data);
+        resolve(data);
+      });
+    }).on('error', function() {
+      reject('Failed to validate this access token with Github.');
+    });
+  });
+}
+
+module.exports = {
+  validateAppId: validateAppId,
+  validateAuthData: validateAuthData
+};