set coursier bootstrap

build.sbt

import scala.sys.process._

lazy val bootstrap = taskKey[Unit]("Create a fat jar file")

bootstrap := {
  // this first publishes the project to ivy local
  publishLocal.value
  val process = Process(
    Seq(
      "coursier",
      "bootstrap",
      "--standalone",
      s"${organization.value}:${name.value}_3:${version.value}",
      "-f",
      "-o",
      s"${name.value}.jar"
    )
  )
  process !
}