Per-user connection concurrency limit does not default to unlimited

Individual connection (not connection group) concurrency limits are intended to be unlimited by default, however the application is enforcing a default per-user concurrency limit of “1”.

Such a limit makes sense for balancing connection groups, where it is important that no individual user can unilaterally exhaust all connections in a group, but it should not apply to connections on their own unless explicitly configured by an administrator.