[669] Display properties keywords for Usage and Definition graphical

node

Bug: eclipse-syson#669
Signed-off-by: Jessy Mallet <jessy.mallet@obeo.fr>

CHANGELOG.adoc

@@ -101,6 +101,7 @@ The source of the edge (the UseCase or Requirement) can be reconnected to anothe
 - https://github.com/eclipse-syson/syson/issues/665[#665] [services] Support public import in direct edit specializations.
 It is now possible to specialize an element with a qualified name containing namespaces importing the required features.
 For example, `myAttribute : ISQ::MassValue` now correctly types the attribute with `ISQBase::MassValue`.
+- https://github.com/eclipse-syson/syson/issues/669[#669] [diagrams] Handle properties keywords in label of Definition and Usage graphical node.
 
 === New features
 

backend/metamodel/syson-sysml-metamodel/src/main/java/org/eclipse/syson/sysml/helper/LabelConstants.java

@@ -71,5 +71,7 @@ public class LabelConstants {
 
     public static final String SUBSETTING = ":>";
 
+    public static final String VARIANT = "variant";
+
     public static final String VARIATION = "variation";
 }