Generate C# SDK with schemas from aidbox URL

[x] Decide what data we need for generating. Do we need to fetch list of packages firstly and then fetch fhir schemas per package, or fetch all schemas in one fetch?
[x] Come up with a solution for retrieving FHIR packages and schemas from Aidbox instance via http (?)
[x] Implement retrieving schemas from Aidbox and using them in SDK generator.

Aidbox / aidbox-sdk