500 because of "Can't create 2 simultaneous Activities"

[johny-b]

(500)
Reason: Internal Server Error
HTTP response headers: <CIMultiDictProxy('Content-Length': '182', 'Content-Type': 'application/json', 'Date': 'Thu, 22 Sep 2022 11:52:26 GMT')>
HTTP response body: {"message":"Service error: Activity 60cc59c13a694c7786f44703f5e00f21 was abruptly terminated. Reason: Only single Activity allowed, message: Can't create 2 simultaneous Activities."}

As discussed with @nieznanysprawiciel, this should probably be 409 Conflict, not 500. This has (ofc) a low priority, although I would probably consume this more specific code in a meaningful way :)