Add an OAuth2 auth provider.

lib/units/auth/oauth2/strategy.js

@@ -0,0 +1,32 @@
+var util = require('util')
+
+var oauth2 = require('passport-oauth2')
+
+function Strategy(options, verify) {
+  oauth2.Strategy.call(this, options, verify)
+  if (!options.authorizationURL) {
+    throw new TypeError('OAuth2Strategy requires a userinfoURL option')
+  }
+  this._userinfoURL = options.userinfoURL
+  this._oauth2.useAuthorizationHeaderforGET(true)
+}
+
+util.inherits(Strategy, oauth2.Strategy)
+
+Strategy.prototype.userProfile = function(accessToken, callback) {
+  this._oauth2.get(this._userinfoURL, accessToken, function(err, data) {
+    if (err) {
+      return callback(err)
+    }
+    else {
+      try {
+        return callback(null, JSON.parse(data))
+      }
+      catch (err) {
+        return callback(err)
+      }
+    }
+  })
+}
+
+module.exports = Strategy