Create a sample Kafka consumer that shows how to parse a DICOM-SR to a set of metadata attributes

One of the important features added to Orthanc during the 0.4 release cycle was parsing of DICOM-SR documents to attributes that could be attached to a resource (either a study or a series) as a comment. When deployed to production, however, we found that the type and variety of DICOM-SR documents received from medical imaging centers quickly overwhelmed the implementation and would result in problems with downstream operations.

To that end, the parser logic has been removed from the Orthanc plugin and attached to this issue. The capability, however, is still something that is needed; but rather than implement it as logic within Orthanc it makes more sense to implement as an add-on that can listen to Kafka and run outside of the application.

Original merge request: orthanc-sonador!37 (merged)