AT:

• reduced code duplication in engineImportMediators
• ideally a unit test of the mediator behavior (it's a crucial part of the import and bugs in e.g. the paging behavior might go unnoticed as we usually test with datasets << max page size)

Note:
The EngineImportMediators in package org.camunda.optimize.service.engine.importing.service.mediator all look very similar. We should try to refactor those classes to reduce code duplication.