Last One Wins with Duplicate Feature Flag Names

[mrm9084]

Description

Fixes: #52

Contribution checklist:

• The pull request does not introduce [breaking changes]
• I have read the contribution guidelines.
• Pull request includes test coverage for the included changes.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR.

[Copilot]

Pull request overview

This PR adjusts feature flag resolution behavior to treat duplicate feature flag ids as “last one wins,” and adds tests to validate the behavior in both sync and async FeatureManager usage.

Changes:

• Update feature flag lookup to prefer the last occurrence when multiple feature flags share the same id.
• De-duplicate list_feature_flag_names() output so duplicate ids are only listed once.
• Add sync and async unit tests covering duplicate-id behavior; add .env to .gitignore.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
featuremanagement/_featuremanagerbase.py	Implements last-one-wins lookup and de-duplicates feature flag name listing.
tests/test_feature_manager.py	Adds sync test asserting last duplicate wins and names are unique.
tests/test_feature_manager_async.py	Adds async test asserting last duplicate wins and names are unique.
.gitignore	Ignores .env files.