Update devcontainer settings

.devcontainer/Dockerfile

@@ -1,10 +1,4 @@
-FROM mcr.microsoft.com/devcontainers/java:8
-
-ARG MAVEN_VERSION=""
-RUN \
-  su vscode -c "umask 0002 && \
-  . /usr/local/sdkman/bin/sdkman-init.sh && \
-  sdk install maven \"${MAVEN_VERSION}\""
+FROM mcr.microsoft.com/devcontainers/java:21
 
 RUN \
   apt-get update && \

.devcontainer/devcontainer.json

@@ -8,37 +8,20 @@
       "NODE_VERSION": "none"
     }
   },
-  "settings": {
-    "workbench.startupEditor": "none",
-    "java.home": "/docker-java-home",
-    "java.import.gradle.java.home": "/usr/local/sdkman/candidates/java/current",
-    "java.configuration.runtimes": [
-      {
-        "default": true,
-        "name": "JavaSE-1.8",
-        "path": "/usr/local/sdkman/candidates/java/current"
-      }
-    ],
-    "files.exclude": {
-      "workspace": true
-    },
-    "java.configuration.updateBuildConfiguration": "automatic",
-    "java.format.settings.profile": "GoogleStyle",
-    "java.format.settings.url": "https://raw.githubusercontent.com/google/styleguide/gh-pages/eclipse-java-google-style.xml",
-    "editor.tabSize": 2,
-    "editor.foldingImportsByDefault": true,
-    "files.trimTrailingWhitespace": true,
-    "git.enableCommitSigning": true
+  "features": {
+    "ghcr.io/devcontainers/features/java:1": {
+      "version": "21"
+    }
+  },
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "vscjava.vscode-java-pack",
+        "vscjava.vscode-maven",
+        "vscjava.vscode-java-test",
+        "editorconfig.editorconfig"
+      ]
+    }
   },
-  "extensions": [
-    "vscjava.vscode-java-pack",
-    "shengchen.vscode-checkstyle",
-    "editorconfig.editorconfig",
-    "pivotal.vscode-boot-dev-pack",
-    "pivotal.vscode-spring-boot",
-    "redhat.vscode-xml",
-    "jebbs.markdown-extended",
-    "davidanson.vscode-markdownlint"
-  ],
-  "remoteUser": "vscode"
-}
+  "postCreateCommand": "mvn clean install"
+}

.vscode/settings.json

@@ -1,11 +1,14 @@
 {
     "github.codespaces.defaultExtensions": [
         "vscjava.vscode-java-pack",
+        "vscjava.vscode-maven",
+        "vscjava.vscode-java-test",
+        "editorconfig.editorconfig",
         "GitHub.codespaces",
         "GitHub.vscode-pull-request-github"
     ],
     "editor.tabSize": 2,
     "scm.showActionButton": false,
     "java.compile.nullAnalysis.mode": "automatic",
     "java.jdt.ls.vmargs": "-XX:+UseParallelGC -XX:GCTimeRatio=4 -XX:AdaptiveSizePolicyWeight=90 -Dsun.zip.disableMemoryMapping=true -Xmx2G -Xms100m -Xlog:disable"
-}
+}