The driver is currently lacking test coverage of the client metadata handshake feature (which the driver has integration logic for, albeit minimal). We should write two smoke tests for this feature, one which uses mongocxx::pool and one which uses mongocxx::client.

The test should perform the following steps:

• Connect to the server with a URI specifying a custom app name ("mongodb://<hostname>/?appName=xyz").
• Run the currentOp command.
• Verify that the currentOp entry associated with the current connection has the expected client metadata. The test should validate at least 1) the correct app name, 2) the correct driver name, 3) the correct mongocxx portion of the driver version, and 4) presence of the "os.type" field.

The assertions for specific client metadata fields other than app name should be skipped on server versions 3.4 and earlier, since SERVER-29075 is not implemented for those versions.