Feat: added get deleted newsletter emails

[Ajinx1]

Description

This pull request introduces a new API endpoint to retrieve soft-deleted newsletters.

Key Features

• Endpoint: GET /api/v1/newsletter-subscription/deleted
• Functionality: Retrieves newsletters that have been soft-deleted.
• Authentication: Requires a valid JWT token for access.
• Authorization: Only users with the SuperAdmin role can access this endpoint.

API DOC HERE

Acceptance Criteria

• The endpoint should accept HTTP GET requests.
• The request must include a valid authentication token in the Authorization header.
• The response should return a list of newsletters that have been marked as soft-deleted.

Authorization Header:

{
    "Authorization": "Bearer <token>"
}

Related Issue

This pull request addresses Issue 288.

How Has This Been Tested?

The changes have been tested with the following methods:

• Integration Tests:
  • Verified successful retrieval of soft-deleted newsletters by an authorized SuperAdmin user.
  • Tested unauthorized access attempts with an invalid token.
  • Handled cases where a regular user attempts to access the endpoint without sufficient permissions.

Screenshots (if appropriate - Postman, etc.)

Types of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• [x] My code follows the code style of this project.
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[Ajinx1]

please remove comments

done