Как выстроить json для post запроса?

Имеется две таблицы как составить json для сохранения в таблицы?

package ru.sibsutis.kitosina.TestExample.entity;

import com.fasterxml.jackson.annotation.JsonIgnore;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*;
import java.util.Date;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
@Table(name = "students")
public class Students {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column
    private Date date;

    @Column
    private String firstName;

    @Column
    private String middleName;

    @Column
    private String lastName;

    @JsonIgnore
    @ManyToOne(fetch = FetchType.LAZY, optional = false, cascade = CascadeType.ALL)
    @JoinColumn(name = "group_name", nullable = false)
    private Group group;

}

package ru.sibsutis.kitosina.TestExample.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*;
import java.util.List;
import java.util.Set;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
@Table(name = "group_info")
public class Group {

    @Id
    private String groupName;

    @Column
    private Integer quantityStudents;

    @OneToMany(mappedBy = "group", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private List<Students> students;
}