Detect which API version an appliance serves

[JonahMMay]

The REST API carries its version in the path — /api/v8.1/... — and nothing negotiates one for the caller, so every consumer has to pick a version up front and hard-code a guess. detect_api_version() removes the guess: it probes /api/v{version}/system/about for each version this package ships and returns the newest one the appliance routes.

That endpoint is the discriminator because it requires a bearer token, so an anonymous probe separates the two cases by status alone: 401 (or 403, or 200 where it is ungated) means the version is served, 404 means routing found nothing. No credentials needed, so it can run before any exist.

Only 8.1 ships today, which makes the answer trivial now and correct later — the candidate list is VERSION_TO_PACKAGE, so adding a version to the package is all it takes for detection to consider it.

Best-effort by contract. Unreachable appliances, proxies that rewrite statuses and anything else unexpected all return None, so a caller falls back to a version of its own choosing instead of failing. Probes run concurrently, so detection costs about one round trip.

detect_rest_api(host) additionally sweeps port x version and returns a RestApiEndpoint(port, api_version), for deployments reached through a port-forwarding proxy rather than on 443.

Also adds pytest-asyncio and a testpaths setting, which the repository needed to run its first tests.