[WIP] Change origin in HTLC messages to be an option

I don't want to use DNL's routing types so I had to just make DNL
support None as origin in all commands, which is interesting because
DNL does accept option<HtlcSource> for addHtlc command but if you use
it, receiveFulfill and all other htlc related functions crash or fail.

Author: aarani

src/DotNetLightning.Core/Channel/ChannelTypes.fs

@@ -283,13 +283,13 @@ type ChannelEvent =
     | WeAcceptedUpdateAddHTLC of newCommitments: Commitments
 
     | WeAcceptedOperationFulfillHTLC of msg: UpdateFulfillHTLCMsg * newCommitments: Commitments
-    | WeAcceptedFulfillHTLC of msg: UpdateFulfillHTLCMsg * origin: HTLCSource * htlc: UpdateAddHTLCMsg * newCommitments: Commitments
+    | WeAcceptedFulfillHTLC of msg: UpdateFulfillHTLCMsg * origin: Option<HTLCSource> * htlc: UpdateAddHTLCMsg * newCommitments: Commitments
 
     | WeAcceptedOperationFailHTLC of msg: UpdateFailHTLCMsg * newCommitments: Commitments
-    | WeAcceptedFailHTLC of origin: HTLCSource * msg: UpdateAddHTLCMsg * nextCommitments: Commitments
+    | WeAcceptedFailHTLC of origin: Option<HTLCSource> * msg: UpdateAddHTLCMsg * nextCommitments: Commitments
 
     | WeAcceptedOperationFailMalformedHTLC of msg: UpdateFailMalformedHTLCMsg * newCommitments: Commitments
-    | WeAcceptedFailMalformedHTLC of origin: HTLCSource * msg: UpdateAddHTLCMsg * newCommitments: Commitments
+    | WeAcceptedFailMalformedHTLC of origin: Option<HTLCSource> * msg: UpdateAddHTLCMsg * newCommitments: Commitments
 
     | WeAcceptedOperationUpdateFee of msg: UpdateFeeMsg  * nextCommitments: Commitments
     | WeAcceptedUpdateFee of msg: UpdateFeeMsg * newCommitments: Commitments

src/DotNetLightning.Core/Channel/CommitmentsModule.fs

@@ -137,7 +137,7 @@ module internal Commitments =
         match cm.GetHTLCCrossSigned(Direction.Out, msg.HTLCId) with
         | Some htlc when htlc.PaymentHash = msg.PaymentPreimage.Hash ->
             let commitments = cm.AddRemoteProposal(msg)
-            let origin = cm.OriginChannels |> Map.find(msg.HTLCId)
+            let origin = cm.OriginChannels |> Map.tryFind(msg.HTLCId)
             [WeAcceptedFulfillHTLC(msg, origin, htlc, commitments)] |> Ok
         | Some htlc ->
             (htlc.PaymentHash, msg.PaymentPreimage)
@@ -178,7 +178,7 @@ module internal Commitments =
                     | false, _ ->
                         msg.HTLCId |> htlcOriginNotKnown
                 let nextC = cm.AddRemoteProposal(msg)
-                return [WeAcceptedFailHTLC(o, htlc, nextC)]
+                return [WeAcceptedFailHTLC(Some o, htlc, nextC)]
             }
         | None ->
             msg.HTLCId |> unknownHTLCId
@@ -216,7 +216,7 @@ module internal Commitments =
                         | false, _ ->
                             msg.HTLCId |> htlcOriginNotKnown
                     let nextC = cm.AddRemoteProposal(msg)
-                    return [WeAcceptedFailMalformedHTLC(o, htlc, nextC)]
+                    return [WeAcceptedFailMalformedHTLC(Some o, htlc, nextC)]
                 }
             | None ->
                 msg.HTLCId |> unknownHTLCId