Slack app built with Scalatra

build.sbt

val ScalatraVersion = "2.7.0"
organization := "hello"
name := "bolt-scalatra-app"
version := "0.1.0-SNAPSHOT"
scalaVersion := "2.13.1"
resolvers += Classpaths.typesafeReleases
libraryDependencies ++= Seq(
  "org.scalatra" %% "scalatra" % ScalatraVersion,
  "com.slack.api" % "bolt-servlet" % "1.0.8",
  "org.scalatra" %% "scalatra-scalatest" % ScalatraVersion % "test",
  "ch.qos.logback" % "logback-classic" % "1.2.3" % "runtime",
  "org.eclipse.jetty" % "jetty-webapp" % "9.4.28.v20200408" % "container",
  "javax.servlet" % "javax.servlet-api" % "3.1.0" % "provided"
)
containerPort in Jetty := 3000
enablePlugins(SbtTwirl)
enablePlugins(ScalatraPlugin)

plugins.sbt

addSbtPlugin("com.typesafe.sbt" % "sbt-twirl" % "1.4.2")
addSbtPlugin("org.scalatra.sbt" % "sbt-scalatra" % "1.0.4")

ScalatraBootstrap.scala

import com.slack.api.bolt.App
import com.slack.api.bolt.handler.builtin.SlashCommandHandler
import com.slack.api.bolt.servlet.SlackAppServlet
import javax.servlet.ServletContext
import javax.servlet.http.{HttpServletRequest, HttpServletResponse}
import org.scalatra._

class RootController extends ScalatraServlet {
  get("/") {
    views.html.hello()
  }
}

class SlackAppController(app: App) extends SlackAppServlet(app) with org.scalatra.Handler {
  override def handle(request: HttpServletRequest, response: HttpServletResponse): Unit = {
    doPost(request, response)
  }
}

object Components {
  lazy val slackApp: App = {
    val app = new App()
    val makeRequestHandler: SlashCommandHandler = (req, ctx) => {
      ctx.ack(s"Thanks <@${req.getPayload.getUserId}>!")
    }
    app.command("/make-request", makeRequestHandler)
    app
  }
}

class ScalatraBootstrap extends LifeCycle {
  override def init(context: ServletContext) {
    context.mount(new RootController, "/*")
    context.mount(new SlackAppController(Components.slackApp), "/slack/events")
  }
}