Support building local docker image

.github/workflows/docker.yml

@@ -0,0 +1,46 @@
+name: Create and publish a Docker image
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup JVM
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: sbt
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Build and push Docker image
+        run: sbt Docker/publish

build.sbt

@@ -3,7 +3,9 @@ inThisBuild(
     scalaVersion      := "3.4.2",
     versionScheme     := Some("early-semver"),
     version           := "3.2",
-    semanticdbEnabled := true // for scalafix
+    semanticdbEnabled  := true, // for scalafix
+    dockerBaseImage    := "openjdk:21",
+    dockerUpdateLatest := true
   )
 )
 
@@ -18,7 +20,7 @@ val chessVersion = "16.0.3"
 
 lazy val `lila-ws` = project
   .in(file("."))
-  .enablePlugins(JavaAppPackaging)
+  .enablePlugins(JavaAppPackaging, DockerPlugin)
   .settings(
     name         := "lila-ws",
     organization := "org.lichess",
@@ -63,7 +65,13 @@ lazy val `lila-ws` = project
       "-Xtarget:21",
       "-Wunused:all"
     ),
-    javaOptions ++= Seq("-Xms32m", "-Xmx256m")
+    javaOptions ++= Seq("-Xms32m", "-Xmx256m"),
+    Docker / packageName      := "lichess-org/lila-ws",
+    Docker / maintainer       := "lichess.org",
+    Docker / dockerRepository := Some("ghcr.io"),
+    Universal / javaOptions := Seq(
+      "-J-Dconfig.override_with_env_vars=true"
+    )
   )
 
 addCommandAlias("prepare", "scalafixAll; scalafmtAll")