2/2: wrap ipa_name in osmo_cni_peer_id with type enum and union

To be prepared for the future in public API, wrap the new osmo_ipa_name struct
in an enum-type and union called osmo_cni_peer.

During code review it was requested to insert an ability to handle different
kinds of peer id, in order to be able to add a Global Title in the future.

Use the generic osmo_cni_peer only in the publicly visible API. For osmo-hlr
internal code, I intend to postpone implementing this into the future, when a
different peer identification actually gets introduced.

This way we don't need to implement it now in all osmo-hlr code paths (save
time now), but still make all external API users aware that this type may be
extended in the future.

Change-Id: Ide9dcdca283ab989240cfc6e53e9211862a199c5
19 files changed