quarkus: MongoClientBuildItem is never produced

Describe the bug MongoClientProcessor has a build method which is supposed to produce MongoClientBuildItem(s) when the relevant Quarkus Mongo configuration is present. I never see the fields in MongodbConfig be anything other than null, hence the build items never get created.

Having MongoClientBuildItem available, is useful for other extensions like the Camel Mongo extension, where it can fetch the client and wire it into the relevant Camel component.

Expected behavior If any of the Mongo configuration options are set, E.g quarkus.mongodb.hosts or quarkus.mongodb.connection-string then a MongoClientBuildItem should be produced.

Actual behavior No MongoClientBuildItem ever seems to be produced, regardless of the Mongo configuration used.

To Reproduce Steps to reproduce the behavior:

1. In your IDE, set a breakpoint in MongoClientProcessor at the start of the build method
2. Launch test BookResourceTest in debug mode
3. Observe conditions for creating MongoClientBuildItem are never satisfied