smp server: refactor subscriptions and delivery in order to always response SOK on subscription with an optional message to follow. (#1573)

* smp server: refactor subscriptions and delivery

* metric for time between MSG and ACK

* cleanup

* refactor pattern match for ghc 8.10.7

* time buckets

* split max time metric

* histogram

* fix

src/Simplex/Messaging/Protocol.hs

@@ -114,6 +114,7 @@ module Simplex.Messaging.Protocol
     BasicAuth (..),
     SrvLoc (..),
     CorrId (..),
+    pattern NoCorrId,
     EntityId (..),
     pattern NoEntity,
     QueueId,
@@ -1370,6 +1371,9 @@ newtype CorrId = CorrId {bs :: ByteString}
   deriving (Eq, Ord, Show)
   deriving newtype (Encoding)
 
+pattern NoCorrId :: CorrId
+pattern NoCorrId = CorrId ""
+
 instance IsString CorrId where
   fromString = CorrId . fromString
   {-# INLINE fromString #-}