libnm: add nm_client_get_main_context() function

The NMClient is associated with a certain context. Add a getter
function to give the context.

The context is really not internal API of NMClient, that is because
the user must iterate this context and be aware of it.

libnm/libnm.ver

@@ -1639,6 +1639,7 @@ global:
 	nm_client_get_context_busy_watcher;
 	nm_client_get_dbus_connection;
 	nm_client_get_dbus_name_owner;
+	nm_client_get_main_context;
 	nm_client_get_metered;
 	nm_client_reload;
 	nm_client_reload_finish;

libnm/nm-client.c

@@ -928,6 +928,32 @@ _nm_client_get_context_dbus (NMClient *self)
 	return NM_CLIENT_GET_PRIVATE (self)->dbus_context;
 }
 
+/**
+ * nm_client_get_main_context:
+ * @self: the #NMClient instance
+ *
+ * The #NMClient instance is permanently associated with the current
+ * thread default #GMainContext, referenced the time when the instance
+ * was created. To receive events, the user must iterate this context
+ * and can use it to synchronize access to the client.
+ *
+ * Note that even after #NMClient instance got destroyed, there might
+ * still be pending sources registered in the context. That means, to fully
+ * clean up, the user must continue iterating the context as long as
+ * the nm_client_get_context_busy_watcher() object is alive.
+ *
+ * Returns: (transfer none): the #GMainContext of the client.
+ *
+ * Since: 1.22
+ */
+GMainContext *
+nm_client_get_main_context (NMClient *self)
+{
+	g_return_val_if_fail (NM_IS_CLIENT (self), NULL);
+
+	return _nm_client_get_context_main (self);
+}
+
 /**
  * nm_client_get_context_busy_watcher:
  * @self: the NMClient instance.

libnm/nm-client.h

@@ -217,6 +217,9 @@ NMClient *nm_client_new_finish (GAsyncResult         *result,
 NM_AVAILABLE_IN_1_22
 GDBusConnection *nm_client_get_dbus_connection (NMClient *client);
 
+NM_AVAILABLE_IN_1_22
+GMainContext *nm_client_get_main_context (NMClient *self);
+
 NM_AVAILABLE_IN_1_22
 GObject *nm_client_get_context_busy_watcher (NMClient *self);