DCAT HVD 2.2.0

[EricSoroos]

Context:

The HVD Spec (https://github.com/SEMICeu/DCAT-AP/tree/master/releases/2.2.0-hvd) has a few specific requirements:

1. The Applicable Legislation ELI (http://data.europa.eu/eli/reg_impl/2023/138/oj) must be applied to Datasets and Distributions(resources) for HVD items. There may be distributions of a dataset that are not covered by the HVD, and they would not contain this value.
2. The HVD Category must be part of a specific codelist.
3. While the HVD profile should be included in the base catalog, there must be a catalog returning only hvd datasets and resources for reporting purposes.

Draft version of HVD 2.2.0 compliance

1. Adds support for codelists as a concept, and uses them for the HVD Category
2. Uses appropriate rdf typing to pass the shaql validation.
3. Provides a read-only profile to provide a HVD only catalog at {base url}/catalog.ttl?profiles=euro_dcat_ap_hvd_220
4. Extracts resource_to_graph into overridable methods.

Todo:

• Shaql validation in automatic testing
• meta link to the HBD only catalog.
• HVD Category rdf is read on import, should be lazy

[EricSoroos]

This is a draft for comment --

• I'm not clear that I'm hooking into the best place to provide the HVD only catalog.
• The resource refactoring is pretty severe to just be able to drop resources out of the graph, there might be a better way.
• I'm also not clear that a narrow subclass is a great idea to provide a minimized catalog, because if it's configured as a default profile, it would remove all non-hvd datasets from the catalog.