How to do @OneToMany on a table that doesn't have a primary key, but has an @EmbeddedId?

Question

Java

There is a table of users employees :
id (primary key) | name | last name
1 | Vasya | Ivanov
2 | Vanya | Petrov
There is a table with attributes for employees employees_attr :
id (from employees) | Attr Name | Attr Value
1 | attr name 1 | attr value 1
1 | attr name 2 | attr value 2
2 | attr name 1 | attr value 1
2 | attr name 2 | attr value 2
This table does not have a primary key (I'm not its author), but there is a unique key id - attr_name
I want to receive in entity for the user the list of its attributes.
I make an entity for employees:

@Table(name = "employees")
public class User {
    @Id
    @Column(name = "id_empl")
    protected Integer id_empl;

    @NotBlank
    @Column(name = "name_employee")
    private String name;
...
   // Так как в employees_attr нет первичного ключа, а JPA требует его, то пришлось сделать @Embeddable
    @OneToMany(mappedBy = "userAttrPK")
    private List<UserAttr> userAttrList;
...}

@Embeddable
public class UserAttrPK implements Serializable {
    @Column(name = "id_empl")
    private int id_empl;

    @NotBlank
    @Column(name = "attr_name")
    private String attrName;
}

@Table(name = "employees_attr")
public class UserAttr {
    @EmbeddedId
    UserAttrPK userAttrPK;

    @NotBlank
    @Column(name = "attr_value")
    private String attrValue;
}

In this scenario, I get an error:

Caused by: org.hibernate.MappingException: Foreign key (FKelqockn69dnn2u8v0kib2m8ik:employees_attr [attr_name,id_empl])) must have same number of columns as the referenced primary key (employees [id_empl])

Here it is clear what he wants, but the structure of the tables is like this.
If the user writes like this:

@OneToMany(mappedBy = "id_empl", fetch = FetchType.EAGER)
    private List<UserAttr> userAttrList;

We'll get an error:

Caused by: org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: ru.....model.UserAttr.id_empl in ru.....dbmaster2.model.User.userAttrList

That is, on the one hand, I need to make a primary key in the attribute table, because this is required by JPA, and on the other hand, a composite primary key is not suitable for linking to a user table.
How can the situation be resolved?