fix(collector): return previous states when the device is disconnected

[palazzem]

Related Issues

• Fixes #148

Proposed Changes

Context: This update enhances the AlarmCoordinator by enabling it to handle device disconnections during state polling and updates more gracefully.

Problem Solved: Previously, a device disconnection led to all binary sensors entering an "Unavailable" state, potentially triggering undesired automations, including false alarm activations. To mitigate this, the update allows the AlarmCoordinator to retain the device's last known state instead of defaulting to "Unavailable" during brief disconnections.

Implementation Details:

• The AlarmDevice now monitors the connection status through a new device.connected attribute.
• This attribute is automatically refreshed once the device reconnects, ensuring the system accurately reflects the current state.

Testing

• Approach: To validate the changes, manually disconnect the device and observe the logs for the expected behavior.
• Expected Outcome: The binary sensors should maintain their last state instead of showing as "Unavailable".

Extra Notes

• Feedback Mechanism: This implementation does not yet offer a direct way to visually confirm the device's connection status outside of log entries. Consequently, implementing issue #139 becomes critical to provide a more intuitive feedback mechanism for users.

Checklist

• [x] Related issues and proposed changes are filled
• [x] Tests are defining the correct and expected behavior
• [x] Code is well-documented via docstrings

[coveralls]

Pull Request Test Coverage Report for Build 8112370177

Details

• 17 of 17 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 93.929%

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Totals
Change from base Build 7977463231:	0.1%
Covered Lines:	669
Relevant Lines:	716

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💛 - Coveralls