[Jetstream] Add MaxBytesPerSubject stream configuration

[kindermoumoute]

Feature Request

Use Case:

When using the stream configurationDiscardPolicy = DiscardNew and DiscardNewPerSubject = true, I want to limit the amount of messages and bytes used per subject. The first one is possible with MaxMsgsPerSubject, the second one is missing.

Proposed Change:

In the stream configuration, add MaxBytesPerSubject - similar to the current MaxMsgsPerSubject.

Alternative Approaches

• Configure only MaxMsgSize and MaxMsgsPerSubject. Cons: force to oversize of the stream.
• Use multiple streams. Cons: not possible to use multiple subject filters.

[derekcollison]

Correct we do not have max bytes per subject atm. And currently do not have any plans for this feature but will review.