Trying to get custom packaging to work...to no avail

models.sbt

lazy val CustomPackage = config("custompackage") extend(Compile) describedAs("Custom package configuration")

mappings in (CustomPackage, packageBin) ~= { (ms: Seq[(File, String)]) =>
  ms filter {
    case (file, toPath) => {
      val shouldInclude = toPath.startsWith("models")
      println("===========" + file + "  " + toPath + " " + shouldInclude)
      shouldInclude
    }
  }
}

lazy val root = project in file(".") overrideConfigs (CustomPackage)