Add Money embeddable value object (corner-scenario enrichment)

src/main/java/com/ankurm/sdjpa4demo/domain/Money.java

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+package com.ankurm.sdjpa4demo.domain;
+
+import jakarta.persistence.Embeddable;
+
+import java.math.BigDecimal;
+
+// A value object: no identity, just its two values. Records make ideal @Embeddable
+// types in Spring Data JPA 4 / Hibernate 7 - immutable, and equals()/hashCode() come free.
+@Embeddable
+public record Money(BigDecimal amount, String currency) {}