Although a many-to-many relationship exists between these entities and stored object,
only one activity or event will ever be linked to a single stored object.
For extra safety measure we return a single result in the repository to ensure our voters
will keep working.
For reusability an AbstractStoredObjectVoter was created and a StoredObjectVoterInterface.
A WorkflowDocumentService checks whether the StoredObject is involved in a workflow.
