Support bundling schemas into Compound Schema Documents

[cfsnyder]

It would be great if this library could also support bundling schemas into Compound Schema Documents. This entails resolving all external references and embedding them as JSON Schema Resources within a single JSON Schema Document. Self-contained schema documents have clear advantages in various use cases.

Here are some relevant resources:

• https://json-schema.org/understanding-json-schema/structuring#bundling
• https://json-schema.org/blog/posts/bundling-json-schema-compound-documents
• https://json-schema.org/draft/2020-12/draft-bhutton-json-schema-01#name-compound-documents

[cfsnyder]

@Stranger6667 If you're in favor of this proposal, I'm happy to work on contributing it!

[Stranger6667]

@cfsnyder

Thanks for opening this! I think most of the functionality is already implemented in the referencing subcrate - it resolves all reachable remote references, so bundling could be done on top of referencing::Registry or somewhere around it.

Somewhat related - #422

I am also glad to hear that you'd like to contribute :) Please, let me know what would be the best way for me to help you with this? Right now, I am working on other things, but I will happily review your PR!

This feature would actually be really useful for jsonschema itself as well - it will simplify some future work on the compiler.

jsonschema::bundle - thinking about this interface

[cfsnyder]

Thanks @Stranger6667! It may be a couple of weeks before I get a chance to tackle this, so I'll get back to you when I have a moment.