feat(rds): MySQL/MariaDB Lambda bridge + prebuilt images

[vieiralucas]

Summary

Aurora MySQL parity for mysql.lambda_async / mysql.lambda_sync. SQL inside an RDS-managed MySQL or MariaDB instance can now invoke fakecloud Lambda functions, mirroring what we shipped for postgres in #806.

• New fakecloud-mysql + fakecloud-mariadb images bake a libcurl-backed UDF (fakecloud_post, fakecloud_post_async) and a bootstrap that creates the Aurora-compatible stored procedures on first start.
• Runtime: ensure_mysql_image / ensure_mariadb_image reuse the postgres pull-first / build-fallback flow via a new shared ensure_bridge_image helper.
• MySQL/MariaDB containers now receive the same FAKECLOUD_* env vars postgres already gets so the bootstrap can render the bridge URL.
• docker-rds-images.yml matrix extended over engine × version × arch (3 engines, 9 version+engine combinations, 2 arches).
• E2E test (rds_mysql_lambda.rs) drives both engines end-to-end.

Test plan

• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --all -- --check
• cargo test -p fakecloud-rds (120 tests)
• cargo test -p fakecloud-e2e --test rds_mysql_lambda (Docker-bound, in CI)
• docker-rds-images.yml PR run exercises mysql + mariadb image builds for both arches

Notes

• The first call to CreateDBInstance with engine=mysql or engine=mariadb will compile the libcurl UDF inside the container the first time the image is built locally; subsequent invocations reuse the cached image. After v0.13.2 publishes, end users will pull the prebuilt image and skip the build entirely.
• Existing MySQL/MariaDB tests that didn't exercise the bridge keep working — only env vars and the image source change.

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Summary by cubic

Adds an Aurora-compatible Lambda bridge for MySQL and MariaDB so SQL can invoke fakecloud Lambda via mysql.lambda_async and mysql.lambda_sync. Ships prebuilt fakecloud-mysql and fakecloud-mariadb images and updates the runtime to pull-first with a local build fallback.

• New Features

  • Prebuilt fakecloud-mysql and fakecloud-mariadb images with a libcurl-backed UDF (fakecloud_post, fakecloud_post_async) and a bootstrap that creates mysql.lambda_async/mysql.lambda_sync.
  • Runtime support: RdsRuntime::ensure_mysql_image and RdsRuntime::ensure_mariadb_image mirror the postgres flow to pull images or build locally.
  • CI: docker-rds-images.yml now builds/publishes postgres/mysql/mariadb across version × arch with tags like <version>-<release> and a rolling <version>.
  • E2E: rds_mysql_lambda.rs covers sync and async invocations on both engines.
  • Docs: README and RDS docs describe the MySQL/MariaDB bridge and image usage.

• Refactors

  • Added shared helpers ensure_bridge_image and bridge_image_tag to centralize pull-first/build-fallback and tagging across engines.
  • MySQL/MariaDB containers now receive FAKECLOUD_* env vars, and bridge-aware engines add the host.docker.internal alias for in-container callbacks.

^{Written for commit 893fa2f. Summary will update on new commits. Review in cubic}

[codecov]

Codecov Report

❌ Patch coverage is 7.74648% with 131 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/fakecloud-rds/src/runtime.rs	7.74%	131 Missing ⚠️

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