Validator for schema

[torhaugl]

Use some validator can be used for both DCAT-AP-NO and our custom schema to ensure data is schema-compliant.

This is to ensure that "illegal" datasets are not uploaded.

[jesper-friis]

Added some domain-specific contexts and requirements files in PR #296

The idea is that the validator uses the requirements.yaml files when validating a schema. This way the the requirements become declarative and separated from the logics.

The format of the requirements.yaml file can be discussed.

We should also have a context validator that ensures that a keyword only is defined once. This should probably be a separate issue.

[torhaugl]

Should we write schema as a SHACL? There exists validators for this

[torhaugl]

Validators for DCAT-AP and DCAT-AP-NO exists. These are both based on SHACL. Are these a good starting point?

Btw, the DCAT-AP-NO one is out-of-date.

[terence-coudert]

Web API for validator explained here https://github.com/ISAITB/validator-resources-dcat-ap/tree/master?tab=readme-ov-file

https://www.itb.ec.europa.eu/shacl/swagger-ui/index.html