chore: add e2e lambda lifecycle test and workflow

[ava-silver]

What does this PR do?

Adds the end-to-end instrumentation lifecycle test for the DatadogLambda construct on AWS Lambda, plus its config, README, and CI workflow. lambda.test.ts drives one CDK stack -- the same physical function throughout -- through the full contract:

1. APPLY -- deploy the bare workload, then redeploy with the construct, instrumenting the function in place; assert config present (pinned Datadog Node + extension layers, redirected handler, DD_* env, identifying tags).
2. TRIGGER -- lambda invoke, then poll the Datadog API until spans and logs carrying the run identity (service/env/version/run id) appear.
3. RE-APPLY -- cdk diff --fail; assert no diff.
4. REMOVE -- cdk destroy; assert the function no longer exists.

e2e.config.ts and versions.ts hold the repo-specific bits: pinned versions, expected layer ARNs, the env/tag contract, and AWS retry patterns. Generic polling and verification come from the shared helpers.

Infrastructure

The "tool under test" is the construct itself (src/), bundled into the CDK app -- not a published package -- so a failure blames the construct. Each run deploys one CloudFormation stack holding a single Lambda; the E2E_INSTRUMENT flag toggles whether the app applies the construct.

flowchart LR
  src["DatadogLambda construct<br/>(src/, under test)"]
  app["CDK app<br/>(esbuild bundle)"]
  ddAcct["Public DD layer account"]
  fn["Workload Lambda"]

  src -->|bundled into| app
  app -->|deploy: bare, then APPLY w/ construct| fn
  ddAcct -->|Node + Extension layers| fn

Loading

The Datadog API key is passed inline to the construct at deploy and surfaces as DD_API_KEY on the function; CI mints it so the workload ships to the org the suite queries. Teardown always runs cdk destroy; the cross-repo sweeper reclaims anything leaked by cancelled CI.

The app is bundled to a single CJS file with esbuild (the repo's TS toolchain is incompatible with ts-node) and run with plain node.

Motivation

Gives the construct a real instrumentation lifecycle test against live AWS + Datadog, so a regression in layer pinning, handler redirect, env wiring, or telemetry flow fails CI.

Testing Guidelines

.github/workflows/e2e.yml runs the suite behind path filters. AWS creds come from OIDC, Datadog creds from dd-sts -- no long-lived secrets, and a missing credential fails loudly rather than skipping green.

Ran the full suite end-to-end locally against the serverless sandbox -- all phases plus teardown pass.

Additional Notes

• Layer/extension versions and the runtime are pinned (overridable via env) so failures blame the construct, not an upstream bump.
• package.json / yarn.lock / .projen/* churn is projen-generated from the .projenrc.js edit (adds vitest, the Datadog API client, and the test:e2e task).

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog

[ava-silver]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• chore: add e2e lambda lifecycle test and workflow #627 👈 (View in Graphite)
• chore: add e2e cdk lambda fixture #626
• chore: add synced e2e shared helpers #625
• main

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