@Entity(name = "invoice")
public class Invoice extends GenericEntity {
    ...
    @ManyToMany
    @JoinTable(name = "invoice_bookings",
        joinColumns = {@JoinColumn(name = "invoice_id", foreignKey = @ForeignKey(name = "fk_invoice_bookings_invoice_id")) },
        inverseJoinColumns = {@JoinColumn(name = "booking_id", foreignKey = @ForeignKey(name = "fk_invoice_bookings_booking_id")) }
    )
    private Collection<PackagePlanBooking> bookings;
    ...
}

@Entity(name = "invoice")
public class Invoice extends GenericEntity {
    ...
    @ManyToMany
    @JoinTable(name = "invoice_bookings",
        joinColumns = {@JoinColumn(name = "invoice_id") },
        inverseJoinColumns = {@JoinColumn(name = "booking_id") }
    )
    @org.hibernate.annotations.ForeignKey(name = "fk_invoice_bookings_invoice_id", inverseName  = "fk_invoice_bookings_booking_id")
    private Collection<PackagePlanBooking> bookings;
    ...
}