Add endpoint to query version

Current situation

There is no way to discover the orchestrator's components' versions. The information is available in the orchestrator logs, but non-admins usually have no access to those logs.

Desired outcome

A new endpoint providing the bill of materials used to build the orchestrator image.

Analysis

We need a BOM.json file, for example at the root of the container. This BOM may be updated or replaced by child images (that choice belongs to the image builders :) ).

A new /version endpoint is added to the observer service. It returns tue usual status message, with a .details.items field containing the BOM information as-is.