Fix msa login account selection (#6400)

Author: shishirx34

src/NuGetGallery/Authentication/Providers/AzureActiveDirectoryV2/AzureActiveDirectoryV2Authenticator.cs

@@ -47,6 +47,7 @@ public static class AuthenticationType
         private static string _callbackPath = "users/account/authenticate/return";
         private static HashSet<string> _errorMessageList = new HashSet<string> { "access_denied", "consent_required" };
         private static HashSet<string> _alternateSiteRootList;
+        private const string SELECT_ACCOUNT = "select_account";
 
         /// <summary>
         /// The possible values returned by <see cref="V2Claims.ACR"/> claim, and also the possible token values to be sent
@@ -214,7 +215,8 @@ private Task AuthenticationFailed(AuthenticationFailedNotification<OpenIdConnect
         }
 
         /// <summary>
-        /// Before redirecting for authentication to the provider, append the properties for Multi-Factor Authentication.
+        /// Before redirecting for authentication to the provider, append the properties for Multi-Factor Authentication
+        /// and configuration settings.
         /// </summary>
         /// <param name="notification">The properties used for authentication</param>
         /// <returns>awaitable Task</returns>
@@ -242,6 +244,9 @@ private Task RedirectToIdentityProvider(RedirectToIdentityProviderNotification<O
                 notification.ProtocolMessage.RedirectUri = "https://" + notification.Request.Uri.Host + "/" + _callbackPath ;
             }
 
+            // We always want to show the options to select account when signing in and while changing account.
+            notification.ProtocolMessage.Prompt = SELECT_ACCOUNT;
+
             return Task.FromResult(0);
         }