MongoDB Unique objectId in document

Question

i want to prevent having the same document data twice EX This is fine

 { _id:objectId("5e693defc65ac2bd8d0c4406"), name: Jhon stage: objectId("5e6929bd725f97bc9a98be3b", day: objectId("5e69298c725f97bc9a98be38") } 

 { _id:objectId("5e693defc65ac2bd8d0c4407"), name: Jhon stage: objectId("5e6929bd725f97bc9a98be3b", day: objectId("5e69298c725f97bc9a98bswe") } 

But i want to prevent this

 { _id:objectId("5e693defc65ac2bd8d0c4406"), name: Jhon stage: objectId("5e6929bd725f97bc9a98be3b", day: objectId("5e69298c725f97bc9a98be38") } 

 { _id:objectId("5e693defc65ac2bd8d0c4407"), name: Jhon stage: objectId("5e6929bd725f97bc9a98be3b", day: objectId("5e69298c725f97bc9a98be38") } 

how can i achive this on mongodb level i mean when making the DB models ?

here is my DB Schema

Stage.add({
      name: {
        type: String,
        unique: true
      },
});

Day.add({
  name: {
    type: Types.Date,
    unique: true
  },
});

  Session.add({
  name: { type: String, default: '', required: true },
  day: {
    type: Types.Relationship,
    ref: 'Day',
    index: true,
  },

  stage: {
    type: Types.Relationship,
    ref: 'Stage',
    index: true,
  },


});