Insufficient implementation in v4.0.1

[DevinXian]

1. Dynamic service registration is not supported in dubbo.ts, services registration is executed only once by init()，which means you have to collect services before dubbo init carefully.
2. May I custom attachments in individual method invoking? such as: traceId, ua, even userId which changes when users make requests.

Ideas above may be incorrect, just for communication. Thank you for the excellent open source contribution!