Add support for FCM custom token (bit 35017)

When sending this message to a peer, the node expects the peer to
link the token with its own pubkey, and use fcm to wake him up
when needed.

eclair-core/src/main/scala/fr/acinq/eclair/io/Peer.scala

@@ -146,6 +146,11 @@ class Peer(val nodeParams: NodeParams, remoteNodeId: PublicKey, watcher: ActorRe
         context.system.eventStream.publish(swapOutResponse)
         stay
 
+    case Event(f: SendFCMToken, d: ConnectedData) =>
+      log.info(s"peer forwarding $f to peerConnection")
+      d.peerConnection ! FCMToken(f.token)
+      stay
+
     case Event(c: Peer.OpenChannel, d: ConnectedData) =>
       if (c.fundingSatoshis >= Channel.MAX_FUNDING && !nodeParams.features.hasFeature(Wumbo)) {
         sender ! Status.Failure(new RuntimeException(s"fundingSatoshis=${c.fundingSatoshis} is too big, you must enable large channels support in 'eclair.features' to use funding above ${Channel.MAX_FUNDING} (see eclair.conf)"))
@@ -486,7 +491,7 @@ object Peer {
 
   case class SendSwapOutRequest(nodeId: PublicKey, amountSatoshis: Satoshi, bitcoinAddress: String, feeratePerKw: Long)
   case class SendSwapInRequest(nodeId: PublicKey)
-
+  case class SendFCMToken(nodeId: PublicKey, token: String)
   // @formatter:on
 
   def makeChannelParams(nodeParams: NodeParams, defaultFinalScriptPubkey: ByteVector, localPaymentBasepoint: Option[PublicKey], isFunder: Boolean, fundingAmount: Satoshi): LocalParams = {

eclair-core/src/main/scala/fr/acinq/eclair/io/Switchboard.scala

@@ -81,6 +81,12 @@ class Switchboard(nodeParams: NodeParams, watcher: ActorRef, relayer: ActorRef,
         case None => sender ! Status.Failure(new RuntimeException("no connection to peer"))
       }
 
+    case f: Peer.SendFCMToken =>
+      getPeer(f.nodeId) match {
+        case Some(peer) => peer forward f
+        case None => log.error(s"could not register fcm token=${f.token} with unknown peer=${f.nodeId}")
+      }
+
     case authenticated: PeerConnection.Authenticated =>
       // if this is an incoming connection, we might not yet have created the peer
       val peer = createOrGetPeer(authenticated.remoteNodeId, offlineChannels = Set.empty)

eclair-core/src/main/scala/fr/acinq/eclair/wire/LightningMessageCodecs.scala

@@ -63,7 +63,7 @@ object LightningMessageCodecs {
   val magic: Codec[Boolean] = recover(constant(hex"fe 47010000"))
 
   // we have limited space for backup, largest message is commit_sig with 30 htlcs in each direction: 65535B - (32B + 64B + 2*30*64B) = 61599B ~= 60000B
-  val channeldataoptional: Codec[Option[ByteVector]] = choice(optional(magic, limitedSizeBytes( 60000, variableSizeBytesLong(varintoverflow, bytes))), provide(Option.empty[ByteVector]))
+  val channeldataoptional: Codec[Option[ByteVector]] = choice(optional(magic, limitedSizeBytes(60000, variableSizeBytesLong(varintoverflow, bytes))), provide(Option.empty[ByteVector]))
 
   val channelReestablishCodec: Codec[ChannelReestablish] = (
     ("channelId" | bytes32) ::
@@ -347,6 +347,9 @@ object LightningMessageCodecs {
 
   //
 
+  val fcmTokenCodec: Codec[FCMToken] =
+    ("fcmToken" | variableSizeBytes(uint16, utf8)).as[FCMToken]
+
   val lightningMessageCodec = discriminated[LightningMessage].by(uint16)
     .typecase(16, initCodec)
     .typecase(17, errorCodec)
@@ -376,15 +379,15 @@ object LightningMessageCodecs {
     .typecase(263, queryChannelRangeCodec)
     .typecase(264, replyChannelRangeCodec)
     .typecase(265, gossipTimestampFilterCodec)
-  // NB: blank lines to minimize merge conflicts
+    // NB: blank lines to minimize merge conflicts
     .typecase(35001, payToOpenRequestCodec)
     .typecase(35003, payToOpenResponseCodec)
-  //
+    //
     .typecase(35005, swapInPendingCodec)
     .typecase(35007, swapInRequestCodec)
     .typecase(35009, swapInResponseCodec)
     .typecase(35015, swapInConfirmedCodec)
-  //
+    //
     .typecase(35011, swapOutRequestCodec)
     .typecase(35013, swapOutResponseCodec)
   //
@@ -393,6 +396,8 @@ object LightningMessageCodecs {
 
   //
 
+    .typecase(35017, fcmTokenCodec)
+
   val meteredLightningMessageCodec = Codec[LightningMessage](
     (msg: LightningMessage) => KamonExt.time(Metrics.EncodeDuration.withTag(Tags.MessageType, msg.getClass.getSimpleName))(lightningMessageCodec.encode(msg)),
     (bits: BitVector) => {

eclair-core/src/main/scala/fr/acinq/eclair/wire/LightningMessageTypes.scala

@@ -374,4 +374,6 @@ case class SwapOutResponse(chainHash: ByteVector32,
 
 //
 
-//
+//
+
+case class FCMToken(token: String) extends LightningMessage