code: func (api UsersAPI) DeleteFacebookAccount(w http.ResponseWriter, r *http.Request) {
  	username := mux.Vars(r)["username"]
  
  	userMgr := user.NewManager(r)
  	err := userMgr.DeleteFacebookAccount(username)
  	if err != nil {
  		log.Error(err)
  		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
  		return
  	}
  
  	w.WriteHeader(http.StatusNoContent)
  }
docs: // DeleteFacebookAccount is the handler for DELETE /users/{username}/facebook
  // Delete the associated facebook account