/// Manager which keeps track of a number of channels and sends messages to the appropriate
/// channel, also tracking HTLC preimages and forwarding onion packets appropriately.
/// Implements ChannelMessageHandler, handling the multi-channel parts and passing things through
/// Manager which keeps track of a number of channels and sends messages to the appropriate
/// channel, also tracking HTLC preimages and forwarding onion packets appropriately.
/// Implements ChannelMessageHandler, handling the multi-channel parts and passing things through