We've already support such dict encoding, we let users register class with an id. And write class by id, id will be encoded as a varint, which uses only 1~5 byt

We've already support such dict encoding, we let users register class with an id. And write class by id, id will be encoded as a varint, which uses only 1~5 bytes. But not every users like the registration. Meta string encoding here is for cases where not mapping is available