Modernize MongoDatabase off legacy com.mongodb.DB API + Testcontainers; rescue disabled MongoDatabaseIT tests

Summary

Two integration tests in src/it/java/dbProcs/MongoDatabaseIT.java are @Disabled and need rescuing:

• getMongoDatabase_ShouldReturnTypeDB
• getMongoDatabase_ReadDbName

They cover MongoDatabase.getMongoDatabase(mongoClient) — that it returns a DB and reads the configured db name (test_shepherdGames).

Why they're disabled

Timeline traced from git history:

• 2022-03-15 (cf57dbfd) — written and passing against Fongo (in src/test/.../MongoDatabaseTest.java).
• 2026-03-28 (f059bb58, "fix: CI pipeline... #801") — moved unit → integration (MongoDatabaseIT.java) and these two tests @Disabled.
• 2026-05-30 (c47c52f5, "feat: add connection pooling... #816") — reason string reworded.

Root cause: Fongo 2.1.1 is incompatible with mongo-java-driver:3.12.14 (NPE in createOperationExecutor). Fongo is unmaintained (last master commit ~2020) and is being dropped entirely in #861.

Why this is its own issue (not part of #861)

#861 is purely the javax.* → jakarta.* namespace migration. Rescuing these tests requires:

1. Bumping mongo-java-driver 3.12.14 → 5.x, and
2. Rewriting MongoDatabase.getMongoDatabase off the legacy com.mongodb.DB API (removed in driver 4.x) onto the modern MongoDatabase type.

That's a production-code change + a major driver upgrade with no relation to the Jakarta namespace. Folding it into #861 would bloat the migration PR and hurt reviewability.

Proposed approach (best practice)

Use Testcontainers MongoDBContainer — the current ecosystem-recommended way to test Mongo in Java (Spring Boot 3 dropped Flapdoodle in favour of Testcontainers; Fongo is effectively deprecated). Requires Docker available in CI.

Work items

• Bump org.mongodb driver 3.12.14 → 5.x.
• Modernize MongoDatabase.getMongoDatabase and callers off the removed com.mongodb.DB API.
• Add org.testcontainers:mongodb (test scope); ensure CI has Docker.
• Re-enable the two tests, restoring the original 2022 assertions:
  • getMongoDatabase_ShouldReturnTypeDB → returns a Mongo database instance.
  • getMongoDatabase_ReadDbName → db name equals test_shepherdGames.
• Remove the @Disabled annotations and their reason strings.

Refs

• #861 (drops the dead Fongo dep; updates the @Disabled reason to point here)
• #801 (where the tests were disabled), #816

Start with src/it/java/dbProcs/MongoDatabaseIT.java and the MongoDatabase.getMongoDatabase method and callers. Review the driver dependency and Testcontainers MongoDB setup first, then re-enable getMongoDatabase_ShouldReturnTypeDB and getMongoDatabase_ReadDbName; done means the modern database type is used and both assertions pass with test_shepherdGames.