have subscriber create-on-demand
Especially communal networks that allow 3rd party SIM cards to camp on the network would
greatly benefit from a subscriber create-on-demand feature in the osmo-hlr. A new subscriber
could be rejected from the network at first, but has then left its IMSI and IMEI in the db.
This implies the ability to disable subscribers even though they are present in the HLR,
otherwise anyone showing up would be authorized immediately, which is usually not desirable.
Clarify whether nam_ps/nam_cs or purge_ps/purge_cs are suitable for this purpose,
otherwise we'd need another flag per subscriber saying 'authorized', which could be false
by default for subscriber create-on-demand.