Populate RegionDetails on failure unconditionally, matching success path

Addresses PR review: the success path (UpdateTelemetry) always calls
CreateRegionDetails, so RegionDetails is non-null even when no region is used
(RegionOutcome.None). Drop the failure-path guard so both paths behave
identically. Updates the non-regional test to assert RegionOutcome.None.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: neha-bhargava

src/client/Microsoft.Identity.Client/Internal/Requests/RequestBase.cs

@@ -14,7 +14,6 @@
 using Microsoft.Identity.Client.Cache.Items;
 using Microsoft.Identity.Client.Core;
 using Microsoft.Identity.Client.Instance.Discovery;
-using Microsoft.Identity.Client.Region;
 using Microsoft.Identity.Client.OAuth2;
 using Microsoft.Identity.Client.TelemetryCore.Internal.Events;
 using Microsoft.Identity.Client.Utils;
@@ -304,7 +303,7 @@ private static AuthenticationResultMetadata CreateFailureMetadata(ApiEvent apiEv
                 CachedAccessTokenCount = apiEvent.CachedAccessTokenCount,
                 CacheRefreshReason = apiEvent.CacheInfo,
                 TokenEndpoint = apiEvent.TokenEndpoint,
-                RegionDetails = apiEvent.RegionOutcome == RegionOutcome.None ? null : CreateRegionDetails(apiEvent),
+                RegionDetails = CreateRegionDetails(apiEvent),
             };
         }
 

tests/Microsoft.Identity.Test.Unit/PublicApiTests/ConfidentialClientApplicationTests.cs

@@ -489,12 +489,13 @@ public async Task ClientCreds_FailedRequest_CarriesFailureMetadata_Async()
                     () => cca.AcquireTokenForClient(TestConstants.s_scope.ToArray()).ExecuteAsync())
                     .ConfigureAwait(false);
 
-                // Assert - the failed attempt still surfaces metadata on the exception. Only data that was
-                // actually captured is populated: the token endpoint was resolved, but no region was
-                // configured so RegionDetails is left null.
+                // Assert - the failed attempt still surfaces metadata on the exception. The token endpoint
+                // was resolved; RegionDetails is populated with RegionOutcome.None (no region configured),
+                // consistent with the success path.
                 Assert.IsNotNull(ex.AuthenticationResultMetadata);
                 Assert.IsNotNull(ex.AuthenticationResultMetadata.TokenEndpoint);
-                Assert.IsNull(ex.AuthenticationResultMetadata.RegionDetails);
+                Assert.IsNotNull(ex.AuthenticationResultMetadata.RegionDetails);
+                Assert.AreEqual(Microsoft.Identity.Client.Region.RegionOutcome.None, ex.AuthenticationResultMetadata.RegionDetails!.RegionOutcome);
             }
         }