feat: added exists and delete functions

[praserx]

This pull request improves the functionality and documentation of the AtomicCache implementation in cache.go and its corresponding tests in cache_test.go. The most significant changes include the addition of new methods for cache management, improvements to comments for clarity, and new test cases to ensure correctness.

New Features:

• Added an Exists method to check if a record is present in the cache and still valid based on its expiration time.
• Added a Delete method to remove a record from the cache, release its memory, and handle empty shards.

Documentation Improvements:

• Fixed typos and improved clarity in comments throughout cache.go, including descriptions for constants, structs, and methods like Set, collectGarbage, and initShardsSection. [1] [2] [3] [4] [5] [6] [7] [8]

Test Enhancements:

• Added a TestCacheExists test to verify the behavior of the new Exists method, including scenarios for unset, set, deleted, and never-set keys.
• Added a TestCacheDelete test to validate the Delete method, ensuring proper deletion behavior and error handling for non-existent keys.

[Copilot]

Pull Request Overview

This PR enhances the AtomicCache functionality by adding new cache management methods and improving documentation clarity. The changes provide essential cache operations that were previously missing and fix various documentation issues.

• Addition of Exists method to check for key presence with expiration validation
• Addition of Delete method to remove keys and handle memory cleanup
• Comprehensive documentation improvements fixing typos and clarifying comments

Reviewed Changes

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

File	Description
cache.go	Implements new Exists and Delete methods, fixes documentation typos and improves comment clarity
cache_test.go	Adds comprehensive test coverage for the new Exists and Delete methods

Comments suppressed due to low confidence (1)

cache_test.go:219

• The test uses TTL of 0 which triggers maximum expiration time (48 hours) according to the Set method documentation. Consider adding explicit tests for this behavior and using a more predictable TTL value for clearer test intent.

	if err := cache.Set(key, data, 0); err != nil {