Removed support to Facebook.

Signed-off-by: cristiano <cristiano.urban@inaf.it>

classes/login/FacebookLogin.php

-<?php
-
-/*
- * This file is part of rap
- * Copyright (C) 2021 Istituto Nazionale di Astrofisica
- * SPDX-License-Identifier: GPL-3.0-or-later
- */
-
-namespace RAP;
-
-class FacebookLogin extends LoginHandler {
-
-    public function __construct(Locator $locator) {
-        parent::__construct($locator);
-    }
-
-    public function login(): string {
-
-        // Retrieve Facebook configuration
-        $Facebook = $this->locator->config->authenticationMethods->Facebook;
-
-        $fb = new \Facebook\Facebook([
-            'app_id' => $Facebook->id,
-            'app_secret' => $Facebook->secret,
-            'default_graph_version' => $Facebook->version,
-        ]);
-
-        $helper = $fb->getRedirectLoginHelper();
-
-        $permissions = ['email']; // Optional permissions: we need user email
-
-        $loginUrl = $helper->getLoginUrl($this->locator->getBasePath() . $Facebook->callback, $permissions);
-
-        return $loginUrl;
-    }
-
-    public function retrieveToken(): string {
-        // Retrieve Facebook configuration
-        $Facebook = $this->locator->config->authenticationMethods->Facebook;
-
-        $fb = new \Facebook\Facebook([
-            'app_id' => $Facebook->id,
-            'app_secret' => $Facebook->secret,
-            'default_graph_version' => $Facebook->version,
-        ]);
-
-        $helper = $fb->getRedirectLoginHelper();
-        if (isset($_GET['state'])) {
-            $helper->getPersistentDataHandler()->set('state', $_GET['state']);
-        }
-
-        // obtaining current URL without query string
-        $accessToken = $helper->getAccessToken($this->locator->getBasePath() . $Facebook->callback);
-
-        if (!isset($accessToken)) {
-            if ($helper->getError()) {
-                $errorMessage = "Error: " . $helper->getError() . "<br>";
-                $errorMessage = $errorMessage . "Error Code: " . $helper->getErrorCode() . "<br>";
-                $errorMessage = $errorMessage . "Error Reason: " . $helper->getErrorReason() . "<br>";
-                $errorMessage = $errorMessage . "Error Description: " . $helper->getErrorDescription();
-                throw new ServerErrorException($errorMessage);
-            } else {
-                throw new BadRequestException("Unable to obtain access token");
-            }
-        }
-
-        // Returns a `Facebook\FacebookResponse` object
-        $response = $fb->get('/me?fields=id,first_name,last_name,email', $accessToken);
-
-        $_SESSION['fb_access_token'] = (string) $accessToken;
-
-        $fbUser = $response->getGraphUser();
-
-        $identity = new Identity(Identity::FACEBOOK);
-        $identity->typedId = $fbUser["id"];
-        $identity->email = $fbUser["email"];
-        $identity->name = $fbUser["first_name"];
-        $identity->surname = $fbUser["last_name"];
-
-        return $this->onIdentityDataReceived($identity);
-    }
-
-}