Use publisher device host fallback for analytics topic hash

[RasmusRynell]

Motivation

• Prevent collisions when callers inject an existing TemporaryAnalyticsMQTTPublisher but do not provide device_config, by allowing topic hashing to use the publisher's device host when available.
• Keep topic generation simple and deterministic while preserving existing behavior when a topic is explicitly provided.

Description

• Add a helper AxisAnalyticsMqttClient._resolve_device_host(...) that returns device_config.host if present, otherwise falls back to publisher.client.device_config.host when an injected publisher exists, and "" as the final fallback.
• Use the resolved host when computing the topic suffix with hash_input = f"{analytics_data_source_key}:{device_host}" so different devices produce different temporary topics.
• Do not change publisher-creation semantics: create_publisher=True still requires device_config, and explicitly provided topic continues to be used as-is.
• Add a focused unit test test_analytics_topic_hash_uses_publisher_device_ip_when_device_config_missing and adjust DummyAnalyticsPublisher/test scaffolding in tests/test_message_processing.py to simulate an injected publisher with a client.device_config.host.

Testing

• Ran python -m compileall src tests, which succeeded and confirmed code compiles.
• Ran PYTHONPATH=src pytest -q tests/test_message_processing.py -k analytics_topic_hash but collection failed due to a missing external dependency (ModuleNotFoundError: No module named 'paho'), so the new unit test could not be executed in this environment.

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Codex Task

[Copilot]

Pull request overview

Adjusts how AxisAnalyticsMqttClient derives its temporary analytics topic to reduce collisions across devices when a publisher is injected without a device_config, by incorporating a resolved device host into the hash input.

Changes:

• Add _resolve_device_host(...) to resolve host from device_config or from an injected publisher’s client device config.
• Update temporary topic suffix hashing to include the resolved host.
• Extend unit tests/scaffolding to validate topic hash behavior across different hosts and publisher-host fallback.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/ax_devil_mqtt/core/manager.py	Incorporates resolved device host into the topic-suffix hash and adds a helper to resolve the host.
tests/test_message_processing.py	Adds dummy device config/publisher scaffolding and new tests covering the new hashing behavior.

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[Copilot]

The added topic-hash tests cover (1) different device_config hosts and (2) fallback to an injected publisher host, but they don’t cover the remaining branch where both device_config and a usable publisher.client.device_config.host are missing. Adding a test for that case would protect the intended fallback behavior and (if desired) enforce backwards-compatible hashing when no host is available.

Suggested change

	assert client_a.topic != client_b.topic
	assert client_a.topic != client_b.topic
	def test_analytics_topic_hash_is_stable_when_no_device_ip_available():
	"""
	When neither device_config nor a usable publisher host is available,
	the topic hash should fall back to the legacy behavior and be stable
	for the same stream key.
	"""
	client_a = AxisAnalyticsMqttClient(
	broker_host="broker",
	broker_port=1883,
	device_config=None,
	analytics_data_source_key="stream-key",
	message_callback=lambda _: None,
	create_publisher=False,
	)
	client_b = AxisAnalyticsMqttClient(
	broker_host="broker",
	broker_port=1883,
	device_config=None,
	analytics_data_source_key="stream-key",
	message_callback=lambda _: None,
	create_publisher=False,
	)
	# With no device IP available from either device_config or publisher,
	# the topic hash should be deterministic and identical for the same
	# stream key, preserving backwards-compatible behavior.
	assert client_a.topic == client_b.topic

[Copilot]

When device_host resolves to an empty string (e.g., device_config=None and no usable host on the injected publisher), the new hash_input = f"{analytics_data_source_key}:{device_host}" changes the computed suffix compared to the previous behavior (sha256(analytics_data_source_key)). This breaks determinism/backwards-compatibility for callers that previously relied on the old hash in the no-host case. Consider only adding the :device_host portion when a non-empty host is available (or otherwise keep the old hashing input when host is empty).

Suggested change

	hash_input = f"{analytics_data_source_key}:{device_host}"
	if device_host:
	hash_input = f"{analytics_data_source_key}:{device_host}"
	else:
	# Preserve previous behavior when no device host is available
	hash_input = analytics_data_source_key