ObjectMessage has an object as payload, ObjectMessageSerializable inherits this and adds serialized_obj.

The former has ~32 bytes in memory, the latter 40.

The goal is not to increase the size of ObjectMessage to 40.

Solution:

• Create an ObjectWrapper class, taking an object and a serialized_version
• This is used in the merged ObjectMessage class (size is still ~32 bytes)
• When we have a SizeStreamable object, we set it as payload, otherwise we create an ObjectWrapper and set it as object.