BC-7772 introduce ddd objects

[CeEv]

Description

• https://github.com/hpi-schul-cloud/schulcloud-server/pull/5167
• https://github.com/hpi-schul-cloud/schulcloud-documentation/pull/38

Links to Tickets or other pull requests

Changes

Datasecurity

Deployment

New Repos, NPM pakages or vendor scripts

Approval for review

• [x] DEV: If api was changed - generate-client:server was executed in vue frontend and changes were tested and put in a PR with the same branch name.
• [ ] QA: In addition to review, the code has been manually tested (if manual testing is possible)
• [x] All points were discussed with the ticket creator, support-team or product owner. The code upholds all quality guidelines from the PR-template.

Notice: Please remove the WIP label if the PR is ready to review, otherwise nobody will review it.