Add WakuMessage version as per spec (#250)

waku/node/v2/waku_types.nim

@@ -24,6 +24,7 @@ type
   WakuMessage* = object
     payload*: seq[byte]
     contentTopic*: ContentTopic
+    version*: string
 
   MessageNotificationHandler* = proc(topic: string, msg: WakuMessage): Future[
       void] {.gcsafe, closure.}
@@ -151,6 +152,7 @@ proc init*(T: type WakuMessage, buffer: seq[byte]): ProtoResult[T] =
 
   discard ? pb.getField(1, msg.payload)
   discard ? pb.getField(2, msg.contentTopic)
+  discard ? pb.getField(3, msg.version)
 
   ok(msg)
 
@@ -159,6 +161,7 @@ proc encode*(message: WakuMessage): ProtoBuffer =
 
   result.write(1, message.payload)
   result.write(2, message.contentTopic)
+  result.write(3, message.version)
 
 proc notify*(filters: Filters, msg: WakuMessage, requestId: string = "") =
   for key in filters.keys:

waku/protocol/v2/waku_store.nim

@@ -16,7 +16,6 @@ logScope:
 const
   WakuStoreCodec* = "/vac/waku/store/2.0.0-beta1"
 
-
 proc encode*(index: Index): ProtoBuffer =
   ## encodes an Index object into a ProtoBuffer
   ## returns the resultant ProtoBuffer