+/// used to retrieve invoices and fulfill invoice requests from [offers]. Currently, only sending
+/// and receiving custom onion messages is supported.
+///
+/// # Example
+///
+/// ```
+/// # extern crate bitcoin;
+/// # use bitcoin::hashes::_export::_core::time::Duration;
+/// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
+/// # use lightning::chain::keysinterface::{InMemorySigner, KeysManager, KeysInterface};
+/// # use lightning::ln::msgs::DecodeError;
+/// # use lightning::ln::peer_handler::IgnoringMessageHandler;
+/// # use lightning::onion_message::{BlindedPath, CustomOnionMessageContents, Destination, OnionMessageContents, OnionMessenger};
+/// # use lightning::util::logger::{Logger, Record};
+/// # use lightning::util::ser::{Writeable, Writer};
+/// # use lightning::io;
+/// # use std::sync::Arc;
+/// # struct FakeLogger {};
+/// # impl Logger for FakeLogger {
+/// # fn log(&self, record: &Record) { unimplemented!() }
+/// # }
+/// # let seed = [42u8; 32];
+/// # let time = Duration::from_secs(123456);
+/// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
+/// # let logger = Arc::new(FakeLogger {});
+/// # let node_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
+/// # let secp_ctx = Secp256k1::new();
+/// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
+/// # let (hop_node_id2, hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1, hop_node_id1);
+/// # let destination_node_id = hop_node_id1;
+/// # let your_custom_message_handler = IgnoringMessageHandler {};
+/// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
+/// // ChannelManager.
+/// let onion_messenger = OnionMessenger::new(&keys_manager, logger, your_custom_message_handler);
+///
+/// # struct YourCustomMessage {}
+/// impl Writeable for YourCustomMessage {
+/// fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+/// # Ok(())
+/// // Write your custom onion message to `w`
+/// }
+/// }
+/// impl CustomOnionMessageContents for YourCustomMessage {
+/// fn tlv_type(&self) -> u64 {
+/// # let your_custom_message_type = 42;
+/// your_custom_message_type
+/// }
+/// }
+/// // Send a custom onion message to a node id.
+/// let intermediate_hops = [hop_node_id1, hop_node_id2];
+/// let reply_path = None;
+/// # let your_custom_message = YourCustomMessage {};
+/// let message = OnionMessageContents::Custom(your_custom_message);
+/// onion_messenger.send_onion_message(&intermediate_hops, Destination::Node(destination_node_id), message, reply_path);
+///
+/// // Create a blinded path to yourself, for someone to send an onion message to.
+/// # let your_node_id = hop_node_id1;
+/// let hops = [hop_node_id3, hop_node_id4, your_node_id];
+/// let blinded_path = BlindedPath::new(&hops, &keys_manager, &secp_ctx).unwrap();
+///
+/// // Send a custom onion message to a blinded path.
+/// # let intermediate_hops = [hop_node_id1, hop_node_id2];
+/// let reply_path = None;
+/// # let your_custom_message = YourCustomMessage {};
+/// let message = OnionMessageContents::Custom(your_custom_message);
+/// onion_messenger.send_onion_message(&intermediate_hops, Destination::BlindedPath(blinded_path), message, reply_path);
+/// ```