remove magic string, fix log formatting (#908)

Author: davidmrdavid

src/DurableWorker/DurableController.cs

@@ -31,7 +31,7 @@ internal class DurableController
         private readonly ILogger _logger;
 
         private bool isExternalDFSdkEnabled { get; } =
-            PowerShellWorkerConfiguration.GetBoolean("ExternalDurablePowerShellSDK") ?? false;
+            PowerShellWorkerConfiguration.GetBoolean(Utils.ExternalDurableSdkEnvVariable) ?? false;
 
         public DurableController(
             DurableFunctionInfo durableDurableFunctionInfo,
@@ -81,7 +81,7 @@ private void tryEnablingExternalSDK()
             else if (isExternalSdkLoaded)
             {
                 // External SDK is in the session, but customer did not explicitly enable it. Report the potential of runtime errors.
-                _logger.Log(isUserOnlyLog: false, LogLevel.Error, String.Format(PowerShellWorkerStrings.PotentialDurableSDKClash, Utils.ExternalDurableSdkName));
+                _logger.Log(isUserOnlyLog: false, LogLevel.Error, String.Format(PowerShellWorkerStrings.PotentialDurableSDKClash, Utils.ExternalDurableSdkName, Utils.ExternalDurableSdkEnvVariable));
             }
         }
 

src/Utility/Utils.cs

@@ -28,6 +28,7 @@ internal class Utils
         internal const string ExternalDurableSdkName = "AzureFunctions.PowerShell.Durable.SDK";
         internal const string IsOrchestrationFailureKey = "IsOrchestrationFailure";
         internal const string TracePipelineObjectCmdlet = "Microsoft.Azure.Functions.PowerShellWorker\\Trace-PipelineObject";
+        internal const string ExternalDurableSdkEnvVariable = "ExternalDurablePowerShellSDK";
 
         internal readonly static object BoxedTrue = (object)true;
         internal readonly static object BoxedFalse = (object)false;