fix: swagger_ui inconsistencies

[eschrewe]

Description

• made edits to various rest controller classes, where the current swagger ui was indicating a response body in error cases
• some minor inconsistency fixes
• solves Swagger UI inconsistent to current behavior for submodel controllers #515

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files
• If helm chart has been changed, the chart version has been bumped to either next major, minor or patch level (compared to released chart).

[tom-rm-meyer-ISST]

LGTM, changes make sense. Also UI still works for changed status codes!