implemented adding/updating of item properties

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

core/src/main/java/de/srsoftware/umbrella/core/model/Property.java

@@ -1,7 +1,6 @@
 /* © SRSoftware 2025 */
 package de.srsoftware.umbrella.core.model;
 
-import static de.srsoftware.tools.Optionals.nullable;
 import static de.srsoftware.umbrella.core.Constants.*;
 
 import de.srsoftware.tools.Mappable;
@@ -45,4 +44,9 @@ public class Property implements Mappable {
 		if (unit  != null) map.put(UNIT,unit);
 		return map;
 	}
+
+	public Property value(Object newVal){
+		value = newVal;
+		return this;
+	}
 }