There are 2 improvements which are made as part of this pull request.
1) The Fixture Builder framework converts all the config properties for Drillbit into string type. But there are certain configurations for authentication (like auth.mechanism) which are expected to be list type. Thus there will be failure during type check. Change to keep collections type config value as is and insert those config value after string types are inserted.
2) The Fixture Builder framework when builds it tries to apply any system options / session options (if set) for which it creates a default client. Hence with cluster enabled for authentication this default client will not provide any connection parameters for authentication and will fail to connect. Allow Fixture Builder to accept client related properties as well so that can be used while creating default client to connect to cluster.