[Backend] Adding the CORS package

[ahmetkudu]

Problem

Currently, the frontend does not redirect to 8000 when a request is made with 3000. To fix this, the CORS package will be installed and implemented.

Solution

Install CORS Package.
Configure CORS in backend code.
Test your application by making a request from port 3000 to see if the redirection to port 8000 now occurs without CORS issues.

Documentation

Report in the pull request description.

Additional notes

No response

Reviewers

Emre Sin

Deadline

14.11.2023 - 23.59

[ahmetkudu]

In the backend, @CrossOrigin(origins = ["*"]) was located near request mappings to reach the endpoints provided with the @PostMapping or @GetMapping annotations. This was a temporary solution for the Milestone 1 presentation. Actually, @CrossOrigin(origins = ["*"]) is a bit problematic in terms of the security. So, the asterisk means the server allows any origin essentially. This is the default setting that developers use for a fully public API. However, we don't let everyone access the endpoint that we have. We only want to be accessed by the users of our platform. We can achieve this issue by using the CORS(Cross-Origin Resource Sharing).

[ahmetkudu]

completed successfully in the pull request.