Feat: remove a subscriber from the newsletter

[Heba-WebDev]

Description

Closes #404

Changes proposed

• Added IsDeleted to NewsLetterSubscriber entity for soft deletion
• Created a migration to apply the IsDeleted column to the database
• Added a base response dto in Hng.Application project under Shared/Dto folder to serve as a general response for both success and failure responses.
• Added DELETE /api/v1/news-letter/:id endpoint to Newsletter controller
• Created a command and a command handler in the Hng.Application project to handle the interface and logic of the endpoint
• Added unit tests for the command handler in the Hng.Application.Test project

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• This PR does not contain plagiarized content.
• The title and description of the PR is clear and explains the approach.
• I am making a pull request against the dev branch (left side).
• My commit messages styles matches our requested structure.
• My code additions will fail neither code linting checks nor unit test.
• I am only making changes to files I was requested to.

Screenshots/Videos

• IsDeleted added after migration
  
  
• Successful response
  
• Bad request returned for invalid id format (Guid)
  
• All tests passing
  

[samuelogboye]

Nice implementation.

I noticed you deleted the initial PR and made another one.

You should'nt do this again.
This means all initial reviews wont be visible in this PR.

When you get on projects, ensure all mistakes are rectified, dont delete issue, PR, Branch.

there are ways in which you can modify your implementation.

Thats is why its Version Control System

[samuelogboye]

LGTM

[Heba-WebDev]

Noted. For next time, I'll make my changes in the same PR.