wip: add skeleton health-check handler

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/GitBridgeServer.java

@@ -129,6 +129,7 @@ public class GitBridgeServer {
 
         HandlerCollection handlers = new HandlerList();
         handlers.addHandler(new StatusHandler(bridge));
+        handlers.addHandler(new HealthCheckHandler(bridge));
         handlers.addHandler(initResourceHandler());
         handlers.addHandler(new PostbackHandler(bridge));
         handlers.addHandler(new DefaultHandler());

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/HealthCheckHandler.java

@@ -0,0 +1,40 @@
+package uk.ac.ic.wlgitbridge.server;
+
+import org.eclipse.jetty.server.HttpConnection;
+import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.server.handler.AbstractHandler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import uk.ac.ic.wlgitbridge.bridge.Bridge;
+import uk.ac.ic.wlgitbridge.util.Log;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public class HealthCheckHandler extends AbstractHandler {
+
+  private final Bridge bridge;
+
+  public HealthCheckHandler(Bridge bridge) {
+    this.bridge = bridge;
+  }
+
+  @Override
+  public void handle(
+    String target,
+    Request baseRequest,
+    HttpServletRequest request,
+    HttpServletResponse response
+  ) throws IOException {
+    if ("GET".equals(baseRequest.getMethod()) && "/health_check".equals(target)) {
+      Log.info("GET <- /api/health_check");
+      baseRequest.setHandled(true);
+      response.setContentType("text/plain");
+      response.setStatus(200);
+      response.getWriter().println("ok");
+    }
+  }
+
+}