Handling watch notifications on the client side. #2
Description
At the moment we have no implementation of watch handling on the client-side.
- Add data structure for watches in session.
- Add API for creation of watches.
- Receive watch notification and order with other requests.
- For read operations check the epoch counter to delay results.
- When reading data, check if it could trigger a watch itself (we read data on which user has watch registered, and the data is newer).