refactoring - guarantee the username is immutable

Author: rcsoyer

src/main/java/org/acme/authorization_server/domain/entity/User.java

@@ -1,5 +1,6 @@
 package org.acme.authorization_server.domain.entity;
 
+import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.validation.constraints.NotBlank;
 import jakarta.validation.constraints.Size;
@@ -9,6 +10,7 @@
 import java.util.Objects;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
+import org.hibernate.annotations.Immutable;
 import org.hibernate.annotations.NaturalId;
 import org.springframework.security.core.CredentialsContainer;
 import org.springframework.security.core.GrantedAuthority;
@@ -31,6 +33,8 @@ public class User extends BaseAuditEntity
     private static final long serialVersionUID = -6086852500553674088L;
 
     @NaturalId
+    @Immutable
+    @Column(updatable = false)
     @NotBlank(message = "The Account username is mandatory")
     @Size(max = 50, message = "The username must be 50 characters or less")
     private String username;