public void addVolume(AbsoluteUnixPath volume) {
      if (volumes == null) {
        volumes = new HashSet<>();
      }
      volumes.add(volume);
    }
Adds a volume entry to the container configuration.

@param volume the absolute path to add as a volume entry
jib-core/src/main/java/com/google/cloud/tools/jib/configuration/ContainerConfiguration.java