When adding or updating sources/mirrors, server was checking if the stream with
a given name exists to check for subject overlaps, among other things.
However, if sourced/mirrored stream was `External`, checks should
not be executed, as not only stream would never be found,
but also, if `External` stream had the same name as the sourcing stream,
the check would be wrongly performed against itself.
Signed-off-by: Tomasz Pietrek <tomasz@nats.io>
We were snappshotting more then needed, so double check that we should be doing this at the stream and consumer level.
At the raft level, we should have always been compacting the WAL to last+1, so made that consistent. Also fixed bug that would not skip last if more items behind the snapshot.
Signed-off-by: Derek Collison <derek@nats.io>
