feat(util): added Docker Util

this component initializes an DockerClient on startup,
then provides a method to run an container with an given image String
and n given Bind-mounts.
This method waits for this container to finish before returning,
so don't call any services that should just be started and left alone!

For this the library github-java-docker is used:
https://github.com/docker-java/docker-java

For this to work, the container this is run in obviously needs
access to the docker socket

src/main/java/de/hftstuttgart/utils/DockerUtil.java

+package de.hftstuttgart.utils;
+
+import com.github.dockerjava.api.DockerClient;
+import com.github.dockerjava.api.command.CreateContainerResponse;
+import com.github.dockerjava.api.model.Bind;
+import com.github.dockerjava.api.model.HostConfig;
+import com.github.dockerjava.core.DefaultDockerClientConfig;
+import com.github.dockerjava.core.DockerClientConfig;
+import com.github.dockerjava.core.DockerClientImpl;
+import com.github.dockerjava.httpclient5.ApacheDockerHttpClient;
+import com.github.dockerjava.transport.DockerHttpClient;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.springframework.core.env.Environment;
+import org.springframework.stereotype.Component;
+
+import java.io.IOException;
+
+@Component
+public class DockerUtil {
+    private static final Logger LOG = LogManager.getLogger(DockerUtil.class);
+
+    private DockerClient dockerClient;
+
+    public DockerUtil(Environment env) {
+        LOG.info("initializing Docker tools");
+        LOG.debug("create docker client config");
+        DockerClientConfig dockerClientConfig = DefaultDockerClientConfig.createDefaultConfigBuilder().build();
+
+        LOG.debug("create docker http client");
+        DockerHttpClient httpClient = new ApacheDockerHttpClient.Builder()
+            .dockerHost(dockerClientConfig.getDockerHost())
+            .sslConfig(dockerClientConfig.getSSLConfig())
+            .build();
+
+        LOG.debug("create docker client");
+        dockerClient = DockerClientImpl.getInstance(dockerClientConfig, httpClient);
+    }
+
+    public int runContainer(String image, Bind... binds) throws InterruptedException, IOException
+    {
+        LOG.debug(String.format("pull image: %s", image));
+        dockerClient.pullImageCmd(image)
+            .start()
+            .awaitCompletion()
+            .close();
+
+        LOG.debug("creating container");
+        CreateContainerResponse containerResponse = dockerClient.createContainerCmd("testcontainer")
+            .withImage(image)
+            .withHostConfig(
+                HostConfig.newHostConfig()
+                    .withBinds(binds))
+            .exec();
+        LOG.debug(String.format("container created: %s", containerResponse.getId()));
+
+        LOG.debug(String.format("starting container %s", containerResponse.getId()));
+        dockerClient.startContainerCmd(containerResponse.getId()).exec();
+
+        LOG.debug(String.format("waiting for completion of container %s", containerResponse.getId()));
+        int ret = dockerClient
+            .waitContainerCmd(containerResponse.getId())
+            .start()
+            .awaitCompletion()
+            .awaitStatusCode();
+        LOG.debug(String.format("container completed with status %d", ret));
+
+        LOG.debug(String.format("deleting container %s", containerResponse.getId()));
+        dockerClient.removeContainerCmd(containerResponse.getId())
+            .withRemoveVolumes(true)
+            .exec();
+
+        return ret;
+    }
+}