feat: manually trigger notification

[alfetopito]

Summary

Add a way to manually trigger the notification clean up.
The cronjob has been added for a few days, but the notifications had not been cleaned up.

Since the strapi cloud logs are quite bad to navigate, this should give instant feedback on what's wrong.

Testing

1. Create a new API token with the permission Notification > cleanup > cleanupExpiredNotifications:
   
2. Make POST request containing the header: authorization: bearer <api key>

• The request should succeed and return the response.

Example of a successful response:

{
    "data": {
        "success": true,
        "deletedCount": 0
    }
}

Example of an error response:

{
    "data": {
        "success": false,
        "error": "This is a test error"
    }
}

[anxolin]

Awesome idea!