🧪 test: Add test coverage for AbstractDiskBasedService.init

[tomdesair]

This commit introduces a new test AbstractDiskBasedServiceTest.java that covers an unexplored error path in the init method of AbstractDiskBasedService. Specifically, it simulates a scenario where Files.createDirectories fails by attempting to create a directory where the parent path is already a file, effectively verifying that the custom StoragePathNotAvailableException is correctly thrown when an invalid storage path is provided.

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PR created automatically by Jules for task 17276221433510533823 started by @tomdesair

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[coveralls]

coverage: 95.154% (+0.2%) from 94.92% — test/abstract-disk-based-service-init-17276221433510533823 into master