Fix identifier as path for cases where file starts with con. causing failures

Author: webprofusion-chrisc

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Globalization;
@@ -1672,7 +1672,18 @@ public async Task<ProcessStepResult> CompleteCertificateRequest(ILog log, Manage
             };
         }
 
-        private string GetIdentifierAsPath(string identifier) => identifier?.Replace("*", "_") ?? "";
+        private string GetIdentifierAsPath(string identifier)
+        {
+            var path = identifier?.Replace("*", "_") ?? "";
+
+            if (path.StartsWith("con."))
+            {
+                // on some versions of windows creating a path with a con. prefix fails.
+                path = path.Replace("con.", "_con.");
+            }
+
+            return path;
+        }
 
         private string GetPrimaryIdentifierAsPath(CertRequestConfig config, string internalId) => GetIdentifierAsPath(string.IsNullOrEmpty(config.PrimaryDomain) ? internalId : config.PrimaryDomain);