[Task] Extend OpenAPI DTOs with metadata from Aspect Model

[MelleD]

Is your task related to a problem? Please describe.

As a developer using the generated REST API,
I want the DTOs generated from the aspect model entities to include additional metadata such as unit or description,
so that clients consuming the API can better understand and utilize the provided data fields.

Describe the solution you'd like
Currently, the REST API provides DTOs and OpenAPI documentation generated from an aspect model and corresponding entities. However, these DTOs do not include field-level metadata such as descriptions or units that are defined in the aspect model.

To improve API usability and documentation quality, an enhancement is requested to include this metadata within the existing DTOs.

One suggested solution is to embed a new inner object (e.g., "metadata" or "attributes") inside each DTO. This object would provide static, field-related metadata