Improve schema modularity

[jonssonchristian]

We have discussed on several occcasions that data for different parts of the data model may be generated by different software tools. It would therefore be useful to publish the JSON Schema in a modular form, so that a tool producing only one part of the EYA DEF can access a JSON Schema for that part only. The Pydantic data models are already modular in that way, and with the current approach of generating the JSON Schema from the Pydantic model, we could easily generate separate schemas for different components. The first task should be to identify the components we think make sense to publish separate JSON Schema for.

A question in relation to this is whether we still want to publish the full data model in a single JSON Schema, or if the top-level JSON Schema can include references to the component schemas.