[ENHANCEMENT] extracted processSubEntities into trait

Extracted the `processSubEntities` into trait, for easier reuse in environments without requests.

__Tasks:__

- [ ] test coverage
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| BC Breaks     | none
| Doc           | none