5-improve-encrypted-storage (#6)

Added the use of DEK's for encryption of secrets. Both the KEK's and DEK's are stored in a way that you can have multiple key of which one is active. But the others are still available for decrypting. This allows for implementing key rotation.

Co-authored-by: eelke <eelke@eelkeklein.nl>
Co-authored-by: Eelke76 <31384324+Eelke76@users.noreply.github.com>
Reviewed-on: #6

IdentityShroud.Core/Security/ConfigurationSecretProvider.cs

@@ -14,4 +14,9 @@ public class ConfigurationSecretProvider(IConfiguration configuration) : ISecret
     {
         return secrets.GetValue<string>(name) ?? "";
     }
+
+    public KeyEncryptionKey[] GetKeys(string name)
+    {
+        return secrets.GetSection(name).Get<KeyEncryptionKey[]>() ?? [];
+    }
 }