修改领域模型。

plusone-basic/plusone-basic-domain/src/main/java/xyz/zhouxy/plusone/domain/ValidatableStringRecord.java

@@ -1,5 +1,7 @@
 package xyz.zhouxy.plusone.domain;
 
+import java.util.Optional;
+
 import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonValue;
 
@@ -31,4 +33,8 @@ public abstract class ValidatableStringRecord implements IValueObject {
     public String toString() {
         return value;
     }
+
+    public static String getValueOrNull(Optional<? extends ValidatableStringRecord> s) {
+        return s.map(ValidatableStringRecord::value).orElse(null);
+    }
 }