API contract
The REST surface as OpenAPI 3.1, and one JSON Schema per type. Because the document is OpenAPI 3.1, those component schemas are JSON Schema 2020-12 — the frontend compiles them into the validators it checks every response with.
main tracks the current code rather than the last release, which is what
a -SNAPSHOT gives you in Maven. Each release is published at its own version, and
the same documents are attached to the GitHub Release.