add healthcheck for kontor-javalin

kontor-javalin/src/main/java/de/thpeetz/kontor/api/Main.java

@@ -2,6 +2,9 @@ package de.thpeetz.kontor.api;
 
 import de.thpeetz.kontor.services.inmemory.InMemoryPersonReader;
 import io.javalin.Javalin;
+
+import java.util.HashMap;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -19,6 +22,11 @@ public class Main {
 
         var app = Javalin.create().start(port);
         app.get("/ping", ctx -> ctx.result("pong"));
+        app.get("/health", ctx -> {
+            HashMap<String, String> status = new HashMap<>();
+            status.put("status", "ok");
+            ctx.json(status);
+        });
         app.get("/persons", ctx -> {
             logger.info("persons called");
             ctx.json(result);