Added warning when using Redis to store Data Protection keys (#36219)

* Add warning when using Redis to store Data Protection keys

Added a warning about using Redis cache to store Data Protection keys, since Redis doesn't persist data across service restarts by default. Provided links for configuration guidance.

* Fix link formatting for Azure Managed Redis documentation

* Update ms.date for key storage providers documentation

---------

Co-authored-by: Wade Pickett <wpickett@microsoft.com>

Author: wcabus

aspnetcore/security/data-protection/implementation/key-storage-providers.md

@@ -3,7 +3,7 @@ title: Key storage providers in ASP.NET Core
 author: tdykstra
 description: Learn about key storage providers in ASP.NET Core and how to configure key storage locations.
 ms.author: tdykstra
-ms.date: 06/11/2025
+ms.date: 11/07/2025
 uid: security/data-protection/implementation/key-storage-providers
 ---
 <!-- ms.sfi.ropc: t -->
@@ -275,6 +275,12 @@ public void ConfigureServices(IServiceCollection services)
 
 :::moniker-end
 
+> [!WARNING]
+> When using Redis to persist data protection keys, be aware that Redis doesn't persist data by default when restarting. This can cause Data Protection to issue new keys, invalidating previously protected data.
+> 
+> You can configure Redis to enable data persistence to mitigate this: Redis documentation has information on [how to configure persistence](https://redis.io/docs/latest/operate/oss_and_stack/management/persistence/).
+> If you're using [Azure Managed Redis](/azure/redis/how-to-persistence), ensure you have enabled data persistence. [Azure Cache for Redis](/azure/azure-cache-for-redis/cache-how-to-premium-persistence?tabs=premium) needs a premium or higher tier to enable data persistence.
+
 For more information, see the following topics:
 
 * [StackExchange.Redis ConnectionMultiplexer](https://github.com/StackExchange/StackExchange.Redis/blob/main/docs/Basics.md)