Mention the passphrase in the BLOB encryption migration steps

docs/en/release-info/migration-guides/abp-10-7.md

@@ -98,14 +98,17 @@ No action is required if you do not enable encryption or configure transforming
 
 If you enable encryption for a container that already contains plaintext BLOBs:
 
-1. Enable encryption with `allowLegacyPlainText: true`.
+1. Enable encryption with `allowLegacyPlainText: true` and configure a passphrase, either for the container or globally with `AbpBlobStoringEncryptionOptions.DefaultPassPhrase`.
 2. Re-save every existing BLOB through the container.
 3. Remove `allowLegacyPlainText` after the migration, so reads fail closed for plaintext content.
 
 ```csharp
-options.Containers.Configure<ProfilePictureContainer>(container =>
+Configure<AbpBlobStoringOptions>(options =>
 {
-    container.UseEncryption(allowLegacyPlainText: true);
+    options.Containers.Configure<ProfilePictureContainer>(container =>
+    {
+        container.UseEncryption(allowLegacyPlainText: true);
+    });
 });
 ```