Adding handling of FAILING_OVER and FAILED_OVER events/push notifications

[petyaslavova]

Pull Request check-list

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• Do tests and lints pass with this change?
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• Is the new or changed code fully tested?
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Description of change

Adding handling of FAILING_OVER and FAILED_OVER events/push notifications

[Copilot]

Pull Request Overview

This PR adds support for handling FAILING_OVER and FAILED_OVER events/push notifications in Redis cluster maintenance operations. These new events complete the failover lifecycle alongside the existing migration events.

• Introduces two new event classes: NodeFailingOverEvent and NodeFailedOverEvent
• Adds a new maintenance state FAILING_OVER to track failover operations
• Extends the existing test infrastructure to validate the complete event lifecycle

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
redis/maintenance_events.py	Adds new failover event classes and FAILING_OVER state, updates handler to support failover events
tests/test_maintenance_events.py	Adds comprehensive test coverage for new failover event classes and updated handler methods
tests/test_maintenance_events_handling.py	Extends integration tests to validate failover events in disabled timeout scenarios and state transitions
tests/test_connection_pool.py	Removes unused import of MaintenanceState

Comments suppressed due to low confidence (2)

tests/test_maintenance_events_handling.py:805

• The test validates that FAILING_OVER events are received but doesn't verify that the maintenance_state is properly updated or that the event handler is called. Consider adding assertions to verify the event handling behavior matches the expected state transitions.

            # Command 5: This SET command will receive FAILING_OVER push message before response

tests/test_maintenance_events_handling.py:825

• Similar to the FAILING_OVER test, this test doesn't verify that the FAILED_OVER event handler is properly called or that maintenance state transitions occur as expected. Consider adding assertions for event handling behavior.

            # Command 7: This SET command will receive FAILED_OVER push message before response

[Copilot]

[nitpick] The comment incorrectly states 'MIGRATED push message' when it should say 'MIGRATED push notification' for consistency with other comments in the same test that use 'push message'.

Suggested change

	# Command 4: This SET command will receive MIGRATED push message before response
	# Command 4: This SET command will receive MIGRATED push notification before response