[REST API] Authentication with Facebook

We need an API that will allow the mobile apps to use the Facebook SDK to authenticate the user, without using the oAuth methods currently being used.

```
            "serviceName": "facebook",
            "accessToken": accessToken,
            "idToken": idToken,
            "expiresIn": Int(expirationDate.timeIntervalSinceNow),
            "scope": "profile"
```