add configuration to use spring-postgres sample with Docker Dev Environments feature

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

spring-postgres/backend/Dockerfile

@@ -1,3 +1,5 @@
+# syntax=docker/dockerfile:1.4
+
 FROM --platform=$BUILDPLATFORM maven:3.8.5-eclipse-temurin-17 AS builder
 WORKDIR /workdir/server
 COPY pom.xml /workdir/server/pom.xml
@@ -5,7 +7,24 @@ RUN mvn dependency:go-offline
 
 COPY src /workdir/server/src
 RUN mvn install
-RUN mkdir  -p target/depency
+
+FROM builder AS dev-envs
+RUN <<EOF
+apt-get update
+apt-get install -y --no-install-recommends git
+EOF
+
+RUN <<EOF
+useradd -s /bin/bash -m vscode
+groupadd docker
+usermod -aG docker vscode
+EOF
+# install Docker tools (cli, buildx, compose)
+COPY --from=gloursdocker/docker / /
+CMD ["mvn", "spring-boot:run"]
+
+FROM builder as prepare-production
+RUN mkdir -p target/dependency
 WORKDIR /workdir/server/target/dependency
 RUN jar -xf ../*.jar