1、The POST Facebook login request must specify the access token in the body of the request.
2、For example, in some countries, if a user does not reply to the opt-in request, he can be regarded as silently accepting the opt-in request.
3、In contrast, in other countries, a system regards a user as an opt-in only when he replied to the opt-in request positively.
4、In this application, the system first sends out an opt-in request notification to users it finds, asking for their communication data upload.
