slapos_web: Fix Facebook login on facebook-sdk 2.0.0

This is a follow up on the API change from the upgrade of facebook-sdk egg from version 0.4.0 to version 2.0.0.

On the version 0.4.0, the GraphAPI was implemented on v2.2 which is not supported anymore by facebook. With this commit we move to use GraphAPI on version v2.7.

master/bt5/slapos_web/ExtensionTemplateItem/portal_components/extension.erp5.ViFiBWeb.py

@@ -74,7 +74,7 @@ def Facebook_getServerToken(self, key):
   return getServerToken(self, key, 'facebook_server_auth_token_cache_factory')
 
 def Facebook_getAccessTokenFromCode(self, code, redirect_uri):
-  return facebook.get_access_token_from_code(code=code,
+  return facebook.GraphAPI(version="2.7").get_access_token_from_code(code=code,
     redirect_uri=redirect_uri,
     app_id=self.portal_preferences.getPreferredVifibFacebookApplicationId(),
     app_secret=self.portal_preferences.getPreferredVifibFacebookApplicationSecret())