Add Spring Boot version to MongoDB driver handshake and append metadata for user-provided clients

[alexbevi]

Enhance Spring Boot's MongoDB client metadata reporting:

• Add driverVersion to the existing MongoDriverInformation in MongoClientFactorySupport, so the handshake includes the Spring Boot version (not just the name) when Spring Boot constructs the MongoClient.

• Append metadata to user-provided clients: When a MongoClient bean is created externally by the user, Spring Boot now calls appendMetadata via reflection at the point it first uses the client — in MongoDatabaseFactoryConfiguration (blocking) and DataMongoReactiveAutoConfiguration (reactive). This ensures MongoDB server-side telemetry registers Spring Boot usage regardless of who constructs the client.

Reflection is used for appendMetadata because it was added in Java driver 5.6.0 and the actual driver version is governed by the Spring Data BOM — older versions skip the call silently.

[nosan]

Including the Spring Boot version alongside the driver name makes the metadata more informative.

However, I don't think Spring Boot should mutate user-provided MongoClient instances. If a user constructs their own client, they should remain responsible for configuring the driver information. For example, I may build a MongoClient with custom driver metadata, and Spring Boot later appending its own metadata via reflection would unexpectedly change that client's configuration.

That feels wrong to me. Spring Boot should enrich metadata only for clients it creates itself, not for externally provided clients.

[alexbevi]

For example, I may build a MongoClient with custom driver metadata, and Spring Boot later appending its own metadata via reflection would unexpectedly change that client's configuration.

Since it's appending it's non-destructive and really only improves the visibility within the mongod or mongos logs (doesn't alter behavior of the MongoClient in any way). It's unlikely driver metadata is being manually configured, as workload identification is typically done by just setting an appName via the connection string.

I do see your point though. If we decide not to proceed a separate PR can be opened to just add the version info.