Add provider data to notifications (#14104)

## Summary

**What** —
Add a providerData field to notifications

**Why** —
We need the ability to pass dynamic fields to specific providers. E.g. CC and BCC for emails

**How** —
Just adding the field to the model

**Testing** —
Added the field to existing tests

## Checklist

Please ensure the following before requesting a review:

- [x] I have added a **changeset** for this PR
    - Every non-breaking change should be marked as a **patch**
    - To add a changeset, run `yarn changeset` and follow the prompts
- [x] The changes are covered by relevant **tests**
- [x] I have verified the code works as intended locally
- [ ] I have linked the related issue(s) if applicable



---

> [!NOTE]
> Adds `provider_data` to notifications (types, workflow input, DB model/migration) and forwards it in the Medusa Cloud Email provider, with tests updated accordingly.
> 
> - **Data/Schema**:
>   - Add `provider_data` (`jsonb`) to `notification` model and DB via migration `Migration20251121150408` and snapshot update.
> - **Types/DTOs**:
>   - Add optional `provider_data` to `CreateNotificationDTO`, `NotificationDTO`, and `ProviderSendNotificationDTO`.
> - **Workflows**:
>   - Extend `send-notifications` step input with `provider_data`.
> - **Providers**:
>   - Medusa Cloud Email: include `provider_data` in outgoing request payload.
> - **Tests**:
>   - Update integration tests to pass and assert `provider_data` propagation.
> - **Changeset**:
>   - Patch bumps for `@medusajs/notification`, `@medusajs/core-flows`, `@medusajs/types`.
> 
> <sup>Written by [Cursor Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit 6f114c75c974a145ef60213637d7c41bc605a0bf. This will update automatically on new commits. Configure [here](https://cursor.com/dashboard?tab=bugbot).</sup>

packages/modules/notification/integration-tests/__tests__/notification-module-service/index.spec.ts

@@ -80,7 +80,8 @@ moduleIntegrationTestRunner<INotificationModuleService>({
           from: "sender@verified.com",
           template: "some-template",
           channel: "email",
-          data: {},
+          data: { link: "http://test.com" },
+          provider_data: { cc: "cc@test.com" },
         } as CreateNotificationDTO
 
         const result = await service.createNotifications(notification)
@@ -91,7 +92,8 @@ moduleIntegrationTestRunner<INotificationModuleService>({
           from: "sender@verified.com",
           template: "some-template",
           channel: "email",
-          data: {},
+          data: { link: "http://test.com" },
+          provider_data: { cc: "cc@test.com" },
           provider_id: "test-provider",
           external_id: "external_id",
           status: NotificationStatus.SUCCESS,

packages/modules/notification/integration-tests/__tests__/notification-module-service/medusa-cloud-email.spec.ts

@@ -20,6 +20,9 @@ const testNotification = {
   data: {
     link: "https://test.com",
   },
+  provider_data: {
+    cc: "cc@test.com",
+  },
 }
 
 moduleIntegrationTestRunner<INotificationModuleService>({
@@ -58,6 +61,9 @@ moduleIntegrationTestRunner<INotificationModuleService>({
             data: {
               link: "https://test.com",
             },
+            provider_data: {
+              cc: "cc@test.com",
+            },
             provider_id: "cloud",
             external_id: "external_id_1",
             status: NotificationStatus.SUCCESS,
@@ -79,6 +85,9 @@ moduleIntegrationTestRunner<INotificationModuleService>({
           data: {
             link: "https://test.com",
           },
+          provider_data: {
+            cc: "cc@test.com",
+          },
         })
       })