feat: Restore User Subscription

[Nainah23]

Fixes Issue/Linear Ticket

This PR addresses an existing issue or a linear ticket.

• Github Issue Example: Closes #ISSUE
• Linear Ticket Example: Fixes ID-ISSUE

Changes Proposed

This section outlines the modifications made in this PR, including file changes, new features, bug fixes, or any dependencies installed.

Summary of Changes

• File Changes:
  • Updated src/controllers/NewsLetterSubscriptionController.ts to include the new API endpoint for restoring deleted newsletter subscriptions.
  • Added new method restoreSubscription in src/services/newsLetterSubscription.service.ts to handle the restoration logic.
  • Updated src/routes/newsLetterSubscription.ts to include the new route for the restore functionality.
  • Modified src/models/newsLetterSubscription.ts to support active/inactive status of subscriptions.
  • Added tests for the restore functionality in newsLetterSubscription.spec.ts, covering success cases, invalid ID scenarios, and unauthorized access.

Notes

• Ensure that the database schema is updated to reflect any changes to the NewsLetterSubscriber model, particularly if isActive field is added.
• Verify that all tests pass successfully after integrating these changes.

Testing

• Success Case: Verified that restoring a valid deleted subscription correctly updates its status to active.
• Invalid ID: Confirmed that attempting to restore with an invalid ID returns an appropriate error response.
• Unauthorized Access: Ensured that unauthorized access to the restore endpoint is correctly denied.

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