fix(app): adding fixed hash bucket and tidying loose ends

[Jacobbrewer1]

Describe your changes

This pull request includes several changes focused on improving error handling, introducing new utility classes, enhancing logging functionality, and refining Kubernetes-related utilities. Below is a categorized summary of the most important changes:

Error Handling Improvements

• Enhanced error handling in the Start method of the App struct by replacing log-based error reporting with explicit error propagation for server and async task initialization issues. (app.go, app.goR203-R245)
• Added a new test case to validate error handling for invalid async task functions in TestApp_Start. (app_test.go, app_test.goL304-R326)

New Utility Classes

• Introduced FixedHashBucket in the cache package, implementing a consistent hashing mechanism for bucket indexing. Includes methods for checking key membership, advancing the bucket index, and retrieving bucket properties. (cache/fixed_hash_bucket.go, cache/fixed_hash_bucket.goR1-R51)
• Added comprehensive tests for FixedHashBucket to validate its functionality, including key distribution and index wrapping. (cache/fixed_hash_bucket_test.go, cache/fixed_hash_bucket_test.goR1-R25)

Logging Enhancements

• Implemented dedupeHandler, a new slog.Handler that deduplicates log attributes. Includes methods for deduplication, grouping, and immutability. (logging/dedupe_handler.go, logging/dedupe_handler.goR8-R26)
• Added unit tests for dedupeHandler to ensure correct deduplication, grouping, and record handling. (logging/dedupe_handler_bench_test.go, logging/dedupe_handler_bench_test.goL13-R134)
• Improved replaceAttrs in logging/logger.go to handle attribute replacement more robustly, including new tests and benchmarks. (logging/logger.go, [1]; logging/logger_test.go, [2]

Kubernetes Utility Updates

• Refined the PodName utility to retrieve the pod name using os.Hostname() as the primary method and falling back to the HOSTNAME environment variable. Added a fallback to an empty string if both methods fail. (utils/kubernetes.go, utils/kubernetes.goL15-R27)

Minor Improvements

• Added a Shutdown method to ServiceEndpointHashBucket for cleaning up resources. (cache/service_endpoint_hash_bucket.go, cache/service_endpoint_hash_bucket.goR147)
• Added interface compliance checks for HashBucket and slog.Handler implementations to ensure type safety. (cache/service_endpoint_hash_bucket.go, [1]; logging/dedupe_handler.go, [2]

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