Added IdProvider

src/main/java/ch/zhaw/gartenverwaltung/io/IdProvider.java

@@ -0,0 +1,11 @@
+package ch.zhaw.gartenverwaltung.io;
+
+public class IdProvider {
+    private long currentId;
+    public IdProvider(long initialValue) {
+        currentId = initialValue;
+    }
+    public long incrementAndGet() {
+        return ++currentId;
+    }
+}