refactor and review

src/users/get_all_users.cpp

@@ -23,13 +23,7 @@ void get_all_users(const httplib::Request &request, httplib::Response &response)
         return;
     }
     jwt::decoded_jwt<jwt::traits::kazuho_picojson> decoded_token = jwt::decode(json_body["token"]);
-    std::string userid;
-    for (std::pair<const std::string, picojson::value> &e: decoded_token.get_payload_json()) {
-        if (e.first == "userId") {
-            userid = e.second.to_str();
-            break;
-        }
-    }
+    std::string userid = decoded_token.get_payload_json()["userId"].to_str();
     if (userid.empty()) {
         response.set_content(STRING403, JSON_TYPE);
         return;