doc(tutorials): enhance tutorial with scenario to integrate a reference solution for app or service

### Description
Feedback from CommDays Dec23:

Initial Scope:
- Include a dummy backend for App (e.g. use reference implementation Umbrella Helm Trace-X solution) to build up tutorial for integration
- High-level overview of required building blocks and how to access the relevant APIs like EDC, DT, ... to start building Apps and Service Solutions as a provider.

### Acceptance Criteria

- [ ] [criteria 1]
- [ ] [criteria 2]
- [ ] [criteria 3]

### Additional Information