Stream state update of servers

// Update implements provider.InstanceGroup.

func (g *instanceGroup) Update(ctx context.Context, update func(instance string, state provider.State)) error {

	servers, err := g.client.Servers.List(ctx, cloudscale.WithTagFilter(g.tagMap()))

	if err != nil {

		return fmt.Errorf("failed to get servers: %w", err)

	}

	for _, server := range servers {

		id := server.UUID

		var state provider.State

		switch server.Status {

		case string(cloudscale.ServerStopped):

			state = provider.StateDeleted

		case string(cloudscale.ServerRunning):

			state = provider.StateRunning

		case "changing":

			state = provider.StateCreating

		}

		update(id, state)

	}

	return nil

}