Add delegation field to type ApplyBlockResult.

This represents any stake delegation discovered when applying a block to
a wallet.

lib/core/src/Cardano/Wallet/Primitive/Model.hs

@@ -67,6 +67,7 @@ import Cardano.Wallet.Primitive.Types
     , EpochLength (..)
     , FeePolicy (..)
     , Hash (..)
+    , PoolId (..)
     , SlotLength (..)
     , SlotParameters (SlotParameters)
     , StartTime (..)
@@ -272,8 +273,10 @@ updateState s (Wallet u tip _ bp) = Wallet u tip s bp
 
 -- | Represents a set of data relevant to a particular wallet, discovered as
 --   the result of applying a block to that wallet.
-newtype ApplyBlockResult = ApplyBlockResult
-    { transactions :: [(Tx, TxMeta)]
+data ApplyBlockResult = ApplyBlockResult
+    { delegation :: !(Maybe PoolId)
+        -- ^ Any stake delegation on behalf of the wallet.
+    , transactions :: ![(Tx, TxMeta)]
         -- ^ The set of transactions that affect the wallet.
     } deriving (Generic, Show, Eq)
 
@@ -290,7 +293,9 @@ applyBlock
     -> (ApplyBlockResult, Wallet s)
 applyBlock (Wallet !u _ s bp) !b =
     ( ApplyBlockResult
-        { transactions = txs }
+        { delegation = Nothing
+        , transactions = txs
+        }
     , Wallet u' (b ^. #header) s' bp
     )
   where