Checking for the completion of one of the fields in the mongo model?

Question

MongoDB

Hai! There is the following model:

const mongoose = require("mongoose");

const UserSchema = new mongoose.Schema({
  name: {
    type: String,
  },
  email: {
    type: String,
    required: true,
    unique: true
  },
  phone: {
    type: String,
    required: true,
    unique: true
  },
  password: {
    type: String,
    required: true
  },
  avatar: {
    type: String
  },
  date: {
    type: Date,
    default: Date.now
  }
});

module.exports = User = mongoose.model("user", UserSchema);

When registering, the user chooses with what he wants to register - email or phone ...
How to describe the fields in the model so that only the filled field is validated during verification?
If you entered the phone, then register using it, or if you entered email, then by email ...