f update docs for forward_htlcs

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -664,7 +664,12 @@ pub(super) struct ChannelHolder<Signer: Sign> {
 	/// here once the channel is available for normal use, with SCIDs being added once the funding
 	/// transaction is confirmed at the channel's required confirmation depth.
 	pub(super) short_to_id: HashMap<u64, [u8; 32]>,
-	/// short channel id -> forward infos. Key of 0 means payments received
+	/// SCID/SCID Alias -> forward infos. Key of 0 means payments received.
+	///
+	/// Note that because we may have an SCID Alias as the key we can have two entries per channel,
+	/// though in practice we probably won't be receiving HTLCs for a channel both via the alias
+	/// and via the classic SCID.
+	///
 	/// Note that while this is held in the same mutex as the channels themselves, no consistency
 	/// guarantees are made about the existence of a channel with the short id here, nor the short
 	/// ids in the PendingHTLCInfo!