Resolve NXCALS-1957 "Entity findallbyid uses get"
#Merge request template @acc-logging-team - please have a look for approval.
Changed GET to POST for findAllByIdIn method. Changed handling of the conflict (added new HTTP status for repeatable conflicts). Fixing NXCALS-1960 ConcurrencyFailureException handled as error
Closes NXCALS-1957