free5GC's BSF concurrent PUT /nbsf-management/v1/subscriptions/{subId} crashes the BSF process via concurrent map read/write on Subscriptions

Summary free5GC's BSF PUT /nbsf-management/v1/subscriptions/subId handler has an unsynchronized write on the global Subscriptions map. The handler first reads the map under RLock via BSFContext.GetSubscriptionsubId, but if the subscription does not exist, ReplaceIndividualSubcription writes back ...