DATACMNS-1122 - Improve message for absent required property in PersistentEntity.getRequiredPersistentProperty(…).

Exception message now contains the property name.

src/main/java/org/springframework/data/mapping/PersistentEntity.java

@@ -151,7 +151,7 @@ public interface PersistentEntity<T, P extends PersistentProperty<P>> extends It
 			return property;
 		}
 
-		throw new IllegalStateException(String.format("Required identifier property not found for %s!", getType()));
+		throw new IllegalStateException(String.format("Required property %s not found for %s!", name, getType()));
 	}
 
 	/**