fix(cache): validate TTL bounds to prevent immediate or infinite expiration (#445)

[Shubham-Gotawade]

Contributed as part of GSSoC '26. Implemented strict input validation boundaries on cache lifetime configurations to eradicate resource leaks and unstable cache states.

Problem Description

Within internal/cache/cache.go, the CacheConfig struct accepted raw time.Duration values for its TTL field without evaluating sanity bounds. Consequently, users or configuration Parsers could supply negative durations, zero durations, or abnormally large parameters.

When zero or negative fields are used, items expire instantly, completely defeating the purpose of the layer and triggering high computational overhead. Conversely, overly massive parameters prevent stale entries from being collected, leaking memory resources indefinitely. Fixes #445.

Solution Implemented

1. Defensive Validation Interceptors: Established architectural bounds for allowable cache lifespans, constraining acceptable parameters between a baseline minimum of 1 minute (1 * time.Minute) and an upper ceiling of 7 days (7 * 24 * time.Hour).
2. Structural Integrity Rules: Integrated validation rules to audit CacheConfig definitions prior to engine initialization. Invalid lifetimes now trigger explicit errors rather than poisoning runtime states.
3. Table-Driven Regression Testing: Introduced complete test matrices inside internal/cache/cache_test.go. The test suite profiles edge cases including negative values (-5m), zero durations (0s), micro-values (10s), standard durations (2h), and out-of-bound configurations (10d) to ensure robust safety guarantees.

Verification & Test Logs

• Local package verification via go test -v ./internal/cache/...: PASSED
• Full workspace baseline compilation via go build ./...: PASSED

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ℹ️ Review info

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Run ID: 54a942d1-e0eb-414c-b612-0122d7fe712e

📥 Commits

Reviewing files that changed from the base of the PR and between 6d6fa89 and 8f33983.

📒 Files selected for processing (2)

• internal/cache/cache.go
• internal/cache/cache_test.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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