add refactoring to signin endpoint

[irfiacre]

What does this PR do?

This PR adds modified files to refactor the sign-in endpoint.

Description of Task to be completed?

• add custom error messages

How should this be manually tested?

• First, you clone the repo on your machine.
• Open the folder in your text editor, preferably visual studio code
• Now open your terminal, for visual studio code just click on terminal
• Now run npm install
• Then run npm run dev,
• After now open postman and run endpoint using POST request localhost:7000/api/auth/v1/signin route;