For bearers using STATIC or DHCP IP method, the modem itself is the one
negotiating authentication with the network. The new `allowed-auth' property
allows users to specify which authentication method(s) are allowed to be used.
See the following NetworkManager commit for more reference:
commit 34aef8aaaa09b7473b9496aa49e550bd2def03f8
Author: Andrew Bird <ajb@spheresystems.co.uk>
Date: Thu Mar 15 16:19:43 2012 -0500
Instead of using a predefined set of string values for 'ip-type' in
Modem.CreateBearer() and Simple.Connect(), we'll use an enumeration. The
implementation will then need to convert the requested IP family type to e.g.
the correct PDP type in 3GPP modems.
This change also consolidates the use of enums in dictionary properties when
possible to do so, as with the Rm Protocol.
