[CO-319] Correctly format (jsend) newtype errors

This is rather ugly and could probably be achieved nicely with a better understanding of the
Generics.SOP library. As far as I could tell, there's no easy way to retrieve 'Tag' for single
constructor

(cf: 'For a datatype with a single constructor we do not need to tag values with their constructor; but for a datatype with multiple constructors we do.  ')

wallet-new/src/Cardano/Wallet/API/V1/Generic.hs

@@ -57,21 +57,21 @@ gtoJsend
     :: forall a. (Generic a, HasDatatypeInfo a, All2 ToJSON (Code a))
     => ResponseStatus -> a -> Value
 gtoJsend rs a = hcollapse $
-    hcliftA2 allpt (gtoJsend' rs)
+    hcliftA2 allpt (gtoJsend' rs (toString $ gconsName a))
     (jsendInfo (Proxy :: Proxy a))
     (unSOP $ from a)
 
 gtoJsend'
     :: All ToJSON xs
-    => ResponseStatus -> JsonInfo xs -> NP I xs -> K Value xs
-gtoJsend' rs (JsonZero n) Nil =
+    => ResponseStatus -> String -> JsonInfo xs -> NP I xs -> K Value xs
+gtoJsend' rs _ (JsonZero n) Nil =
     jsendValue rs (Tag n) (Object mempty)
-gtoJsend' rs (JsonOne tag) (I a :* Nil) =
-    jsendValue rs tag (toJSON a)
-gtoJsend' rs (JsonMultiple tag) cs =
+gtoJsend' rs consName (JsonOne _) (I a :* Nil) =
+    jsendValue rs (Tag consName) (toJSON a)
+gtoJsend' rs _ (JsonMultiple tag) cs =
     jsendValue rs tag . Array . V.fromList . hcollapse $
     hcliftA pt (K . toJSON . unI) cs
-gtoJsend' rs (JsonRecord tag fields) cs =
+gtoJsend' rs _ (JsonRecord tag fields) cs =
     jsendValue rs tag . Object . HM.fromList . hcollapse $
     hcliftA2 pt (\(K field) (I a) -> K (toText field, toJSON a)) fields cs