Корректный, хоть и грубый захват JSON'а

src/endpoints_handlers/AuthRegistrationExecutor.h

@@ -31,18 +31,35 @@ public:
     using namespace boost::beast;
 
     auto body = req.body();
-    object json_as_object = json::parse(body).as_object();
+    value req_json;
 
-    std::string login = json_as_object.at("login").as_string().c_str();
+    try
-    std::string password = json_as_object.at("password").as_string().c_str();
+    {
+      req_json = json::parse(body);
+    }
+    catch (const system::system_error& err)
+    {
+      http::response<ResponseType> res{http::status::bad_request, req.version()};
+
+      res.body() = "{ \"detail\": \"cannot deserialize json\"}";
+      res.set(http::field::content_type, "application/json");
+      res.content_length(res.body().size());
+
+      return res;
+    }
+
+    std::string login = req_json.as_object().at("login").as_string().c_str();
+    std::string password = req_json.as_object().at("password").as_string().c_str();
+
+    if (user_dao_->GetByLogin(login).has_value())
+    {
+    }
 
     User user;
 
     user.SetLogin(login);
     user.SetPassword(password);
 
-    user_dao_->GetByLogin(login);
-
     http::response<ResponseType> res{
         http::status::ok, req.version()
       };