Decouple FFE from Tracing proposal

[PerfectSlayer]

What Does This Do

This PR introduces a dedicated module for FFE config.
This would avoid adding :internal-api or :dd-trace-api into the :feature-flagging-api module and keep the separation between FFE and Tracing clean.

Motivation

Configuration will be generated at some points from the JSON configuration.
This is an intermediate solution that will keep the FFE design clean.

Additional Notes

This PR is a change proposal as part of the review of #11658

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Jira ticket: [PROJ-IDENT]

[leoromanovsky]

Works for me, thanks!

[pavlokhrebto]

thank you!

[chatgpt-codex-connector]

💡 Codex Review

https://github.com/DataDog/dd-trace-java/blob/d3f54ffd72a758ade9b021dafa6011be5b9147e1/dd-trace-api/src/main/java/datadog/trace/api/config/FeatureFlaggingConfig.java#L1
Preserve the old FeatureFlaggingConfig API

When a customer or external integration upgrades dd-trace-api and still imports datadog.trace.api.config.FeatureFlaggingConfig for these public config keys, deleting the class makes their source stop compiling; reflective/runtime lookups of the old class also fail. The replacement is in a new product module that dd-trace-api does not publish or depend on, so please keep a deprecated forwarding class in the old package (or provide another compatibility path) while moving internal users to the new module.

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[datadog-datadog-prod-us1]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 56.97% (-0.01%)

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🔗 Commit SHA: 4b4b1c2 | Docs | Datadog PR Page | Give us feedback!}

[PerfectSlayer]

When a customer or external integration upgrades dd-trace-api and still imports datadog.trace.api.config.FeatureFlaggingConfig for these public config keys, deleting the class makes their source stop compiling; reflective/runtime lookups of the old class also fail.

I’m good with that. It’s experimental keys and I don’t want to add api project(":feature-flaggging-config") into the :dd-trace-api that has no other dependencies than a logger.

[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	13.98 s	13.91 s	[-0.3%; +1.2%] (no difference)
startup:insecure-bank:tracing:Agent	12.95 s	13.06 s	[-1.8%; -0.0%] (maybe better)
startup:petclinic:appsec:Agent	16.90 s	16.75 s	[-0.2%; +2.0%] (no difference)
startup:petclinic:iast:Agent	16.94 s	16.89 s	[-0.5%; +1.2%] (no difference)
startup:petclinic:profiling:Agent	16.62 s	16.90 s	[-2.7%; -0.7%] (maybe better)
startup:petclinic:sca:Agent	16.86 s	16.74 s	[-0.3%; +1.7%] (no difference)
startup:petclinic:tracing:Agent	16.03 s	16.12 s	[-1.4%; +0.4%] (no difference)

Commit: 4b4b1c26 · CI Pipeline · Benchmarking Platform UI

---

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

[mcculls]

LGTM