Summary

Implements the QUERY HTTP method as defined in RFC 10008 — a safe, idempotent method that carries a request body to express a query predicate.

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.