fixed Dockerfile for Gitpod Classic

Author: meysholdt

.devcontainer/Dockerfile

@@ -0,0 +1,5 @@
+# Not actually used by the devcontainer, but it is used by gitpod
+FROM gitpod/workspace-full
+
+ARG JAVA_VERSION=17.0.7-ms
+RUN bash -c ". /home/gitpod/.sdkman/bin/sdkman-init.sh && sdk install java $JAVA_VERSION && sdk use java $JAVA_VERSION"

.gitpod.Dockerfile

@@ -1,4 +1,5 @@
-image: gitpod/workspace-full
+image: 
+  file: .gitpod.Dockerfile
 
 tasks:
   - init: ./mvnw clean install -U -DskipTests