[#12048] Migrate Get Instructors Action

[domlimm]

Part of #12048.

Things to highlight

Not sure if it is the best way to do this (similar to PR #12211):

EntitysData data = new EntitysData();
List<EntityData> entityDataList = entitysForCourse
        .stream()
        .map(EntityData::new)
        .collect(Collectors.toList());

data.setEntitys(entityDataList);

As EntitysData class current constructor with EntityAttribute will cause a type erasure problem when adding another constructor taking in a List of different data type.