Expand error message when submit challenge fails

Author: webprofusion-chrisc

src/Certify.Providers/ACME/Anvil/AnvilACMEProvider.cs

@@ -1303,7 +1303,7 @@ public async Task<StatusMessage> SubmitChallenge(ILog log, string challengeType,
                 }
                 catch (AcmeRequestException exp)
                 {
-                    var msg = $"Submit Challenge failed: {exp.Error?.Detail}";
+                    var msg = $"Submitting the challenge response to the Certificate Authority failed. This may indicate a temporary fault in their system: {exp.Error?.Type} {exp.Error?.Detail}";
 
                     log?.Error(msg);