Add Spring Data + Document DB Playground

[hossain-rayhan]

Add Spring Data MongoDB playground (Java)

Summary

Adds a fifth playground — spring-data-mongodb — demonstrating Spring Boot + Spring Data MongoDB (Java) against a local DocumentDB emulator. This extends the repository into the JVM ecosystem, complementing the existing Node.js (Mongoose / native driver) and Python (Beanie / PyMongo) playgrounds. It follows the exact structure and conventions of the existing playgrounds.

What's included

• Lifecycle scripts (scripts/) mirroring the other playgrounds — lib.sh, start-documentdb.sh, stop-documentdb.sh, run-app.sh, run-test.sh — adapted to a Maven/JDK toolchain (instead of npm/venv), including a resolve_maven helper that prefers ./mvnw and falls back to system mvn.
• Spring Boot demo API exposing the same surface as the sibling playgrounds:
  • Book @Document model with a compound index and @CreatedDate/@LastModifiedDate auditing
  • BookRepository (MongoRepository) with a derived query
  • REST endpoints: POST/GET/PATCH/DELETE /books, GET /books/{id}, GET /stats/genres (aggregation), GET /health
• Standalone 16-step compatibility suite (CrudCompatibilityTest) using MongoTemplate: connect, index creation, insert (single/many), findById, filtered/sorted queries, count, update, findAndModify, aggregation, unique-index enforcement, delete, and $vectorSearch.
• Documentation: a playground README.md matching the house style, plus updates to the root README.md (playground table, quick-start example, repository layout).

Java-specific TLS handling

Unlike the Node.js/Python drivers, the MongoDB Java driver has no connection-string option to accept a self-signed certificate — tlsInsecure only disables hostname verification, not certificate-chain validation. To connect to the emulator's self-signed cert, MongoClientFactory installs a trust-all SSLContext (gated by TLS_INSECURE) and strips replicaSet / tlsAllowInvalidCertificates from the shared connection string. For production, set TLS_INSECURE=false and configure a truststore with the server's CA.

Validation

• mvn compile succeeds.
• Compatibility suite prints Passed: 16 Failed: 0 against documentdb-local:latest.
• Demo API verified manually: /health returns healthy, book creation populates auditing timestamps + generated id, listing works, and /stats/genres aggregation returns expected results.

How to try it

cd playgrounds/spring-data-mongodb
./scripts/run-test.sh   # start DocumentDB locally and run the compatibility suite
./scripts/run-app.sh    # or run the demo REST API on :3000

Prerequisites: Docker, JDK 17+, and Maven.