perf(feature_flags): validate schema once per fetched document

[dreamorosi]

Issue number: closes #8426

Summary

Changes

FeatureFlags.get_configuration() now skips schema validation when the store hands back the same document object it validated last time. A new document is always validated, so the "always validate fresh configuration" guarantee is unchanged; the only work removed is repeat validation of an unchanged, cached document.

The check is object identity (config is self._last_validated_config). The Parameters cache stores the transformed dict and returns that same object on every hit until max_age expires (parameters/base.py, fetch_from_cache), so identity is a faithful signal for "same fetch". FeatureFlags keeps a strong reference to the last validated document, so its id() cannot be recycled by an unrelated object. Third-party StoreProvider implementations that return a fresh dict per call get today's behaviour: validation on every call.

AppConfigStore with an envelope would have defeated the check on its own, since the JMESPath query produces a new object each call. The store now memoises the extracted result against the raw document's identity, so envelope users get the same benefit.

Failed validation is not cached: _last_validated_config is only assigned after validate() returns, so an invalid document raises on every call as before.

Tests cover: one validation across five evaluate calls plus get_enabled_features; re-validation when the store returns a new document and no re-validation when it returns the same one again; invalid documents raising on every call and not poisoning the cache; and the envelope path returning the same extracted object and validating once.

User experience

No API or behavioural change for evaluate, get_enabled_features, or get_configuration. Return values are identical.

For a handler evaluating N flags per invocation against a cached document, schema validation runs once per cache refresh instead of N times per invocation. The saving scales with document size (features x rules x conditions).

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.65%. Comparing base (a39e101) to head (1953c1b).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8431   +/-   ##
========================================
  Coverage    96.65%   96.65%           
========================================
  Files          296      296           
  Lines        14767    14778   +11     
  Branches      1246     1248    +2     
========================================
+ Hits         14273    14284   +11     
  Misses         359      359           
  Partials       135      135           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.