Register a MemCube

curl --request POST \
  --url https://api.example.com/mem_cubes \
  --header 'Content-Type: application/json' \
  --data '
{
  "mem_cube_name_or_path": "/path/to/cube",
  "user_id": "user123",
  "mem_cube_id": "cube123"
}
'

{
  "message": "Operation successful",
  "code": 200,
  "data": null
}