feat(rds): support PostgreSQL aws_lambda extension (#800)

[vieiralucas]

Closes #800.

Summary

• Lets SQL inside fakecloud-managed RDS PostgreSQL instances invoke fakecloud Lambda functions via the AWS RDS aws_lambda extension shape — same surface LocalStack documents, same return tuple (status_code, payload, executed_version, log_result).
• New fakecloud-postgres:<major>-<hash> image is built lazily off postgres:<major> the first time a Postgres DB instance is created. The image bakes in plpython3u, aws_commons, and aws_lambda. Hashed tag invalidates cached images when fakecloud changes the embedded extension files.
• New bridge endpoint POST /_fakecloud/rds/lambda-invoke is what plpython3u calls. It builds an account-scoped ARN and dispatches through the existing LambdaDelivery trait. invocation_type=Event returns 202 immediately and runs the Lambda async.
• Postgres containers now get --add-host host.docker.internal:<bridge> plus FAKECLOUD_ENDPOINT / FAKECLOUD_ACCOUNT_ID / FAKECLOUD_REGION env vars so the python UDF can find fakecloud across macOS, Linux, and Windows hosts.

User-visible:

CREATE EXTENSION IF NOT EXISTS aws_lambda CASCADE;
SELECT aws_commons.create_lambda_function_arn('my_function');
SELECT * FROM aws_lambda.invoke('my_function', '{"body":"Hello!"}'::json);

Test plan

• cargo build -p fakecloud clean
• cargo clippy --workspace --all-targets -- -D warnings clean
• cargo fmt --all
• cargo test -p fakecloud-rds passes (119 tests)
• cargo test -p fakecloud-e2e --test rds_aws_lambda -- --nocapture (CI — needs Docker; first run builds the postgres image which takes ~60s)
• README, website RDS docs, website service grid synced

---

Summary by cubic

Adds PostgreSQL aws_lambda extension support in fakecloud RDS so SQL can invoke fakecloud Lambda functions. Ships a lazy-built fakecloud-postgres:<major>-<hash> image with plpython3u, aws_commons, and aws_lambda, plus a bridge endpoint to route calls.

• New Features

  • Invoke Lambda from SQL via aws_lambda.invoke(...) and aws_commons.create_lambda_function_arn(function_name, region), returning (status_code, payload, executed_version, log_result).
  • Lazy-built fakecloud-postgres image per major version; content-hashed tag auto-invalidates the cache.
  • Bridge POST /_fakecloud/rds/lambda-invoke resolves account-scoped ARNs and routes through existing Lambda delivery; invocation_type=Event returns 202 and runs async.
  • Postgres containers add host.docker.internal and set FAKECLOUD_ENDPOINT/FAKECLOUD_ACCOUNT_ID/FAKECLOUD_REGION for cross-OS connectivity.
  • Docs updated; E2E test covers sync and async paths.

• Bug Fixes

  • aws_commons.create_lambda_function_arn second parameter is region; composite field names aligned. Composite aws_lambda.invoke wrapper switched to LANGUAGE SQL and now honors the ARN’s region.
  • aws_lambda.invoke (plpython3u) preserves HTTP status codes when the bridge response lacks status_code.
  • E2E test binds json payloads as SQL literals due to tokio-postgres lacking the serde_json feature.
  • TypeScript RDS e2e timeout increased to 180s for the first-run Postgres image build; formatted with Prettier.

^{Written for commit 447b5de. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

3 issues found across 15 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="crates/fakecloud-rds/assets/postgres/aws_lambda--1.0.sql">

<violation number="1" location="crates/fakecloud-rds/assets/postgres/aws_lambda--1.0.sql:52">
P2: HTTP error responses can lose their real status code and return `0` when the error JSON omits `status_code`.</violation>
</file>

<file name="crates/fakecloud-rds/assets/postgres/aws_commons--1.0.sql">

<violation number="1" location="crates/fakecloud-rds/assets/postgres/aws_commons--1.0.sql:13">
P1: Use a `region` field here instead of `qualifier`; this helper is meant to carry the Lambda region, not a version/alias.</violation>
</file>

<file name="website/content/docs/services/rds.md">

<violation number="1" location="website/content/docs/services/rds.md:74">
P2: Don't claim AWS parity here; fakecloud only implements a subset of the RDS Lambda API and its helper signature differs from AWS.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[codecov]

Codecov Report

❌ Patch coverage is 0% with 220 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/fakecloud-rds/src/runtime.rs	0.00%	123 Missing ⚠️
crates/fakecloud-server/src/main.rs	0.00%	91 Missing ⚠️
crates/fakecloud-rds/src/service.rs	0.00%	6 Missing ⚠️

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