Merge #1992

1992: Add user advice to `UnableToDetermineCurrentEpoch` error. r=jonathanknowles a=jonathanknowles

# Issue Number

#1939 

# Overview

This PR revises the error we show if we cannot determine the current epoch, inviting the user to wait and try again.

# Comments

Ideally, we'd be able to give the user some indication of _how long_ they should wait, but assuming we cannot reliably know this information, letting them know that waiting may resolve the issue is arguably better than giving no advice at all.


Co-authored-by: Jonathan Knowles <jonathan.knowles@iohk.io>

lib/core/src/Cardano/Wallet/Api/Server.hs

@@ -1997,8 +1997,10 @@ showT = T.pack . show
 instance LiftHandler ErrCurrentEpoch where
     handler = \case
         ErrUnableToDetermineCurrentEpoch ->
-            apiError err500 UnableToDetermineCurrentEpoch
-                "I'm unable to determine the current epoch."
+            apiError err500 UnableToDetermineCurrentEpoch $ mconcat
+                [ "I'm unable to determine the current epoch. "
+                , "Please wait a while for the node to sync and try again."
+                ]
 
 instance LiftHandler ErrUnexpectedPoolIdPlaceholder where
     handler = \case