Abstract
This PR contains a bug fix for the issue described here.
Details
The reference to a value managed by the shared pointer escapes (Line 30).
https://github.com/tier4/scenario_simulator_v2/blob/fa9ca062dfd0cb5ca6ea55ae28d29c8935dee668/external/concealer/include/concealer/subscriber.hpp#L21-L56
When that const & is used and the underlying value is modified by the owner, a race condition occurs.
Return by value instead of by const & to force a copy and avoid the problem.
References
Regressions OK