Parse features on UFC splits

[danyal002]

Warning

NOT READY FOR REVIEW YET

What Does This Do

• Adds a Feature class (key, value) to the UFC model in the bootstrap module.
• Adds a nullable features list to Split. Each feature has a key, a value, and a list of destinations. The existing constructor still works.
• Registers a lenient FeatureListAdapter in UniversalFlagConfigParser:
  • A value that is not a list becomes null.
  • The adapter drops an entry that is not an object, has a missing or empty key, or has a value that is not a string, number or boolean.
  • The adapter keeps every non-empty string destination, including unknown ones, and drops a feature with no destinations.
  • The flag still parses in every case.

Motivation

The UFC will carry features on some splits, starting with holdout splits (holdout.key, holdout.assignment_group). Customers who write exposures to their own warehouse need these values in their exposure hook. This change only parses them. A later change surfaces them in flag metadata.

A malformed feature must not reject the flag, because features never change which variation a subject gets.

Additional Notes

• Split ships in the bootstrap module with dd-java-agent, so an older agent has no features field. The change that first reads the field will guard it the way DDEvaluator.splitSerialIdSupported guards serialId.
• Configurations without features parse as before.

Jira ticket: EX-3799

[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.89 s	13.87 s	[-0.6%; +0.9%] (no difference)
startup:insecure-bank:tracing:Agent	12.88 s	12.94 s	[-1.2%; +0.3%] (no difference)
startup:petclinic:appsec:Agent	17.12 s	16.99 s	[+0.0%; +1.6%] (maybe worse)
startup:petclinic:iast:Agent	16.94 s	16.94 s	[-0.8%; +0.8%] (no difference)
startup:petclinic:profiling:Agent	16.62 s	16.74 s	[-1.7%; +0.3%] (no difference)
startup:petclinic:sca:Agent	17.06 s	16.92 s	[+0.1%; +1.6%] (maybe worse)
startup:petclinic:tracing:Agent	16.14 s	16.08 s	[-0.4%; +1.2%] (no difference)

Commit: 4197807a · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.