[CORE-3630] cert client

[hemarkus]

Checklist

• [x] Commits are reasonably small, easy to follow, and only concern one topic or task
• [x] Commit messages are descriptive and include more details in the body if necessary
• [x] Acceptance criteria including constraints are present in the ticket or linked
• [x] There is no communication or clarifications that has not been added to the ticket
• [ ] No further unit tests need to be added or updated
• [ ] No further component test cases need to be adjusted
• [x] The specification and documentation are up-to-date with the implementation
• [x] Link to Pull Request is added to the ticket (Add Tickets to title)