make CSN compilation work at runtime

[swennemers]

The ORD endpoint should be able to return the resource definitions for every API/event not only during build but also at runtime.

As part of this issue, fix the error reported in the linked issues.

[swennemers]

Need conceptual alignment with @stewsk and CAP team, how to have access to right CSN mode also at runtime, when the CAP framework typically has only the optimized CSN model available.

Related issues #147

[mlakov]

@swennemers , @stewsk - ins't this one done via #157 ?

[stewsk]

ins't this one done via #157 ?

No. #157 just applies some transformations to those parts of the CSN that describe a data product.
This is completely unrelated to how the CSN is obtained in the first place.