* Fix cache serialisation
* fix(cache): add integer overflow protection for serialization
- [x] Add maxCacheEntrySize constant (64 MiB) to prevent memory overflow
- [x] Validate byte slice size before adding marker byte
- [x] Validate JSON-serialized data size before marker addition
- [x] Add comprehensive overflow protection test cases
* docs: add security fix documentation for integer overflow protection
* test: fix goroutine tests to use mock OIDC servers
The TestContextAwareGoroutineManagement tests were making real HTTP
calls to hardcoded URLs like https://example.com, causing failures
in CI when those requests timeout or return HTTP errors.
Changes:
- Added createMockOIDCServer() helper function using httptest
- Updated GoroutineCleanupOnContextCancel to use mock server
- Updated NoGoroutineLeakOnMultipleInstances to use 3 mock servers
- Updated SingletonTasksAcrossInstances to use mock servers array
This prevents network calls and makes tests more reliable and faster.
Fixes test failures in GitHub Actions CI.
