[BUG]Regular users are able to open submited solutions by other users

[karastoyanov]

Describe the bug
Every regular user can open the submited solutions for the other users. The chance is very low due to the random submission id generated in the backend logic, however a bugfix is needed.

To Reproduce
Steps to reproduce the behavior:
N/A

Expected behavior
Limit the user's access to the submited solutions. Only the admins and the author of the solution should be able to open the solution.

[karastoyanov]

Form reworked with a0f4a0f