origin: Add API to query supported protocols

This will allow selecting a suitable origin when placing outgoing calls.

plugins/ofono/calls-ofono-origin.c

@@ -101,6 +101,16 @@ dial (CallsOrigin *origin, const gchar *number)
 }
 
 
+static gboolean
+supports_protocol (CallsOrigin *origin,
+                   const char  *protocol)
+{
+  g_assert (protocol);
+  g_assert (CALLS_IS_OFONO_ORIGIN (origin));
+
+  return g_strcmp0 (protocol, "tel") == 0;
+}
+
 CallsOfonoOrigin *
 calls_ofono_origin_new (GDBOModem *modem)
 {
@@ -576,6 +586,7 @@ static void
 calls_ofono_origin_origin_interface_init (CallsOriginInterface *iface)
 {
   iface->dial = dial;
+  iface->supports_protocol = supports_protocol;
 }