feat: download and preview of certificate PDFs

[Jatewo]

Description

This PR adds the functionality for downloading/previewing certificate PDFs.

Changes

• Added onClick to ActionButton for download and preview functions
• Added on click functions and a preview object element to certificate cards
• Added _id to contentCreator interface
• Fixed overflow behaviour for certificate list
• Added tests

Related Issues

List any related issues or tickets that this pull request addresses or resolves.

Checklist

• [x] Code has been tested locally and passes all relevant tests.
• [x] Documentation has been updated to reflect the changes, if applicable.
• [x] Code follows the established coding style and guidelines of the project.
• [x] All new and existing tests related to the changes have passed.
• [x] Any necessary dependencies or new packages have been properly documented.
• [x] Pull request title and description are clear and descriptive.
• [x] Reviewers have been assigned to the pull request.
• [x] Any potential security implications have been considered and addressed.
• [x] Performance impact of the changes has been evaluated, if relevant.

Screenshots (if applicable)

If mobile/frontend pull request, what version of the backend is it stable, and running on?

Branch: dev

Commit: 39b3576

Notes for Reviewers

Run the cert-test-pdf-download branch to test this. This branch is temporary and the same goes for the fact that requests are send to a student-certificates endpoint - this will be fixed as soon as the functionality has been fully implemented.