Currently the only real way of using contrib modules or custom libs with the SolrCloud resource is to provide a custom solr.xml, or to build a somewhat custom docker-image that already has these libraries loaded into the default libs directories. Using a custom solr.xml is very much discouraged, so it would be nice to support this common, and recommended use case, by default.

Starting with #301 , we are now loading in contrib modules for users. It would be great to have two additional fields for the SolrCloud CRD:

• SolrCloud.spec.additionalLibs : []string - A list of directories to load in the classpath
• SolrCloud.spec.contribModules : []string - A list of contrib modules to load in the classpath. This could be done explicitly with the additionalLibs option, but it would be nice to offer this convenience option for users so they don't have to understand the filesystem layout of the Solr docker image.

Note that we would also probably want to auto-load contrib modules that are required by other parts of the CRD. So when a user want to use a GCS repository for backups, the Solr Operator will auto-add the gcs-repository contrib to the classpath without the user having to specify it.