fix relation enum declaration

src/main/java/com/mercateo/common/rest/schemagen/link/relation/RelationEnum.java

@@ -1,8 +1,12 @@
 package com.mercateo.common.rest.schemagen.link.relation;
 
-public interface RelationEnum<E extends Enum<E> & RelationEnum<E>> extends RelationContainer {
+public interface RelationEnum extends RelationContainer {
+
+    public String name();
+
     @Override
     default public Relation getRelation() {
-        return Relation.of(((Enum<?>)this).name().toLowerCase().replace('_', '-'));
+        return Relation.of(name().toLowerCase().replace('_', '-'));
     }
+
 }

src/test/java/com/mercateo/common/rest/schemagen/link/relation/RelationEnumTest.java

@@ -5,7 +5,7 @@
 import org.junit.Test;
 
 public class RelationEnumTest{
-    enum TestRelation implements RelationEnum<TestRelation>{
+    enum TestRelation implements RelationEnum{
         TEST_RELATION
     }