intellij idea buddy plugins spring data jpa + rest repositories

Question

entity Class Project

@ManyToOne(optional = false)
@JoinColumn(name = "manager_id", nullable = false)
private AppUser manager;

i have a problem when i create AppUserRepositories post json :

{
    "name":"deoakw12",
    "manager":{
        "id":"1"
    },
    "tasks":[
        {
            "name":"oooo",
            "assignee":{
                "id":"2"
            }
        },
        {
            "name":"oooo1",
            "assignee":{
                "id":"2"
            }
        }
    ]

}

message

"not-null property references a null or transient value : com.jpa.buddy.entities.Project.manager"