Topic consumer permissions

[alexv-smirnov]

Currently it's possible to grant granular permissions to YDB users to read from a particular topic. If there are several subscribing users which have to read all messages from the same topic, they need to use different consumer names.

But there's no mechanism to ensure that different users do not use an incorrect consumer name, so any user who is granted read permission on a topic can affect the operation of another users with the same privileges, if using the incorrect consumer name, accidentally or not.

To ensure the users using consumer names correctly, there must be a special privilege and corresponding authorisation to use the particular consumer name under some user account.