@Data
@Entity
@Table(name = "employees")
public class Employee extends Parent {

    // other attributes


    @ManyToMany(cascade = {CascadeType.ALL})
    @JoinTable(
            name = "employees_projects",
            joinColumns = {@JoinColumn(name = "employee_id")},
            inverseJoinColumns = {@JoinColumn(name = "project_id")}
    )
    Set<Project> projects = new HashSet<Project>();


}




@Data
@Entity
@Table(name = "projects")
public class Project extends Parent{

   
    // other attributes

    @ManyToMany(mappedBy = "projects", cascade = {CascadeType.ALL})
    private Set<Employee> employees = new HashSet<Employee>();

}