Motivation

FFE SDK consumers have fixture cases that are not present in the canonical ffe-system-test-data repo. Before migrating consumers to git submodules, the canonical source needs to include those shared cases with linked evidence showing where each migrated fixture came from.

Changes

• Add normalized null-targeting-key fixture coverage.
• Add normalized numeric ONE_OF default-path fixture coverage from existing consumer fixture files.
• Rename the migrated Java/.NET test-case-race-conditions.json fixture to test-case-numeric-one-of-default.json because the fixture validates default behavior, not concurrency.
• Update README and CONTRIBUTING to describe downstream submodule consumption and fixture contribution rules.

Decisions

• Treat consumer-owned JSON fixtures as the source of truth for this catch-up PR.
• Normalize migrated fixtures to the canonical schema by adding explicit targetingKey, attributes, result.value, and result.reason fields where older consumer fixtures omitted them.
• Use descriptive canonical fixture names even when source repos had stale or misleading filenames.
• Keep PHP out of the consumer list until its OpenFeature client lands.

Evidence

• test-case-null-targeting-key.json comes from dd-trace-go: https://github.com/DataDog/dd-trace-go/blob/5fd6d9c4d6f7c1718cbada1a91923fe1622e5f3f/openfeature/testdata/evaluation-cases/test-case-null-targeting-key.json#L1-L40
• The same null-targeting-key fixture also exists in libdatadog: https://github.com/DataDog/libdatadog/blob/866d7c8a1eed40ab5b9ee46e7de924cdf304ce91/datadog-ffe/tests/data/tests/test-case-null-targeting-key.json#L1-L40
• test-case-numeric-one-of-default.json is the canonical name for Java's original test-case-race-conditions.json: https://github.com/DataDog/dd-trace-java/blob/710ca8758317ee5c09c15bb2e0f5808b75fc1b5f/dd-smoke-tests/openfeature/src/test/resources/data/test-case-race-conditions.json#L1-L10
• The same source fixture also exists in dd-trace-dotnet as test-case-race-conditions.json: https://github.com/DataDog/dd-trace-dotnet/blob/42c4df9daa4d3583142d6c12d2292f90410df015/tracer/test/Datadog.Trace.Tests/FeatureFlags/resources/data/test-case-race-conditions.json#L1-L10

Validation

• Validated JSON syntax for ufc-config.json and every evaluation-cases/*.json file.
• Verified every fixture flag references a flag present in ufc-config.json, except the intentional missing-flag fixture.
• Verified every evaluation case has targetingKey, attributes, result.value, and result.reason.
• Downstream consumer PRs load this repository as a submodule and loop over evaluation-cases/*.json.