feat(front): Make invitation work

Making inviation of teacher work with new design.

How to test:

• Create a course
• Click invite users
• Write your username and click send
• Then refresh the page
• Click on the mail icon and click at the reques

Based on !64 (merged) & !42 (merged)

Closes #73 (closed)!

Screenshot_2024-04-12_at_01.56.01