Number of unread messages

[sanmiguel2019]

Is your feature request related to a problem? Please describe.

Users who use Tinode with rest auth may need to know the number of unread messages for each user to show this number on a parent application. Now the ony way to do this is to subscribe to me topic but this loads a huge amount of unnecessary data (avatars, user agents, etc, etc, that need processing, calculating.

Describe the solution you'd like

1. get message could have what option like unread that returns only readId and seqId for each topic, probably without a need to attach, to make things much easer.
2. Tinode could store/increase the number of unread messages in the memory and reset it when user interacts in a client.