Standardize all messages between components and modules

[Haigutus]

1. Use JSON-LD
2. Use DCAT as basis https://www.w3.org/TR/vocab-dcat-3/#dcat-scope
3. Use pydantic or something similar to validate messages and also parse/serialize the messages

Possible issues, pydantic does not support direclty JSON-LD, but json schema, so maybe another lib needs to be used or we need to switch from JSON-LD to json schema or even go back to XML/XSD setup, ala https://pypi.org/project/xsdata-pydantic/

[Haigutus]

related to #85