osmo-sgsn: add VTY parameter to toggle authentication

It may be useful to have 'remote' authorization policy, but do not
require authentication in GERAN at the same time, e.g. in combination
with 'subscriber-create-on-demand' feature of OsmoHLR.

This change introduces a new VTY parameter similar to the one
that we already have in OsmoMSC:

  authentication (optional|required)

Please note that 'required' only applies if 'auth-policy' is 'remote'.

Change-Id: I9909145e7e0af587c28827e16301a61b13eedaa9
3 files changed