Several issues that need to be paid attention to in proto3

1. When using the kratos framework, if the structure in the proto uses a nested structure, when the http service is used, the field in the nested structure cannot be obtained, and it can only be the default value of the field type

//在请求的参数结构体中，只能使用这种最简单的方式，不能嵌套
message LoginRequest {
  string username = 1;
  string password = 2;
}

2. When returning data, if a field has no value, this field will not be visible in the returned structure