Follow up to 8674 - Basic implementation of `isEditAllowed` is probably not sufficient for some classes

[JonasCir]

Bug Description

While working on #8674, I noticed some inconsistencies around isEditAllowed specifically the implementation in:

• CampaignService.java where a basic implementation was added which needs to be verified if anything else needs to be done
• CaseService.java which only contains a basic implementation which is far less sophisticated than the checks for e.g., contacts which looks suspicious.

Investigate the logic and make sure that it is correct and no bugs are introduced by the basic implementation.