Persistence model depends on public management API

### Describe the bug

All entities of the persistence model have `asXyz()` functions to return a type from the management OpenAPI spec. While this is currently convenient, it introduces a cyclic dependency, which should generally be avoided:
* management-API depends on REST endpoints
* REST endpoint implementations depend on entities
* entities depend on management-API

The management API and its implementation should not leak into the persistence model.

### To Reproduce

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### Actual Behavior

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### Expected Behavior

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### Additional context

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### System information

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