feat(config): add global proxy configuration

the previously deleted set proxy from JGitUtil was just...meh

This checks if we got a proxy set in the properties file
Additionally the user can provide a list of not-proxy hosts.
This setup will then check, if a proxy is available and if so,
make sure it only gets used if the uri is not on the not-proxy list.

src/main/java/de/hftstuttgart/config/ProxySetup.java

+package de.hftstuttgart.config;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.Environment;
+
+import java.io.IOException;
+import java.net.*;
+import java.util.*;
+import java.util.stream.Collectors;
+
+@Configuration
+/**
+ * Configures Proxy once on startup
+ */
+public class ProxySetup extends ProxySelector
+{
+    private static final Logger LOG = LogManager.getLogger(ProxySetup.class);
+
+    List<Proxy> noProxy;
+    List<Proxy> setProxy;
+    Set<String> noProxyHosts;
+
+    public ProxySetup(Environment env) {
+
+        String ignoredHostNames = env.getProperty("proxy.ignoredHostNames");
+        if (Objects.isNull(ignoredHostNames)) {
+            ignoredHostNames = "";
+        }
+
+        String proxy = env.getProperty("proxy");
+
+        LOG.info("Configuring Proxy");
+        noProxy = Collections.singletonList(Proxy.NO_PROXY);
+
+        if (Objects.nonNull(proxy)) {
+            String[] proxyValues = proxy.split(":");
+            Proxy p = new Proxy(
+                Proxy.Type.HTTP,
+                new InetSocketAddress(proxyValues[0], Integer.parseInt(proxyValues[1])));
+            setProxy = Collections.singletonList(p);
+
+            LOG.info(String.format("set proxy: %s", p.address().toString()));
+        }
+
+        noProxyHosts = Arrays.stream(ignoredHostNames.split(","))
+            .map(String::toLowerCase)
+            .collect(Collectors.toCollection(HashSet::new));
+
+        LOG.info(String.format("Hosts to be ignored: %s", noProxyHosts));
+
+        ProxySelector.setDefault(this);
+    }
+
+    @Override
+    public List<Proxy> select(URI uri) {
+
+        LOG.debug(String.format("Proxy selection for URI: %s", uri.getHost()));
+
+        // No proxy for given hosts
+        if (noProxyHosts.contains(uri.getHost().toLowerCase())) {
+            LOG.debug(String.format("Proxy disabled for host %s", uri.getHost()));
+            return noProxy;
+        }
+
+        // no proxy if no proxy was set
+        if (Objects.nonNull(setProxy)) {
+            LOG.debug(String.format("Proxy used for host %s", uri.getHost()));
+            return setProxy;
+        }
+
+        LOG.debug("No proxy configured to choose from");
+        return noProxy;
+    }
+
+    @Override
+    public void connectFailed(URI uri, SocketAddress socketAddress, IOException e) {
+        LOG.error(String.format("connection to %s failed with %s", uri.getHost(), e.getMessage()));
+    }
+}