fix(API): enforce lower case feature names on the backend

[bardock-2393]

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Changes

Closes #8171

Project.only_allow_lower_case_feature_names is a project setting (on by default) that's supposed to require feature names to be lower case. Until now it was only ever enforced client-side by the web app, so anyone creating a feature directly via the API (curl, a script, an SDK) could give it a mixed-case name even when the project setting says otherwise.

This PR makes the backend enforce the same rule when a feature is created via the API, so the setting means what it says regardless of which client is used.

How did you test this code?

Added unit tests covering:

• Project.is_feature_name_valid with only_allow_lower_case_feature_names on and off, combined with the existing regex check.
• The feature creation endpoint returning a 400 with a clear error message when the name isn't lower case, still returning 201 for lower-case names, and still allowing mixed-case names when the project setting is disabled.

Also updated a handful of pre-existing tests that happened to create features with mixed-case names against the default project (where the setting is on), so they now use lower-case names.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 1719ea28-50fe-44a6-979e-1cb53f00600f

📥 Commits

Reviewing files that changed from the base of the PR and between 10a3bb7 and 24235c3.

📒 Files selected for processing (4)

• api/features/serializers.py
• api/projects/models.py
• api/tests/unit/features/test_unit_features_views.py
• api/tests/unit/projects/test_unit_projects_models.py

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📝 Walkthrough

Walkthrough

Feature creation now rejects uppercase characters when lower-case-only feature names are enabled. Project validation applies the same rule before the optional regular expression check. Unit tests cover lower-case, mixed-case, and uppercase names, including the disabled setting. Existing feature fixtures now use lower-case names.

Estimated code review effort: 2 (Simple) | ~10 minutes

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Fix failing CI checks

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