+/// A handler provided to [`PeerManager`] for reading and handling custom messages.
+///
+/// [BOLT 1] specifies a custom message type range for use with experimental or application-specific
+/// messages. `CustomMessageHandler` allows for user-defined handling of such types. See the
+/// [`lightning_custom_message`] crate for tools useful in composing more than one custom handler.
+///
+/// [BOLT 1]: https://github.com/lightning/bolts/blob/master/01-messaging.md
+/// [`lightning_custom_message`]: https://docs.rs/lightning_custom_message/latest/lightning_custom_message