Поскольку он мог бы выдавать список ссылок на другой документ в node.js

const userSchema = new Schema({
  email: {
    type: String,
    match: /^\S+@\S+\.\S+$/,
    required: true,
    unique: true,
    trim: true,
    lowercase: true
  },
  password: {
    type: String,
    required: true,
    minlength: 6
  },
  name: {
    type: String,
    index: true,
    trim: true
  },
  role: {
    type: String,
    enum: roles,
    default: 'user'
  },
  picture: {
    type: String,
    trim: true
  },

  alumnos:[{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'AlumnoRes' 
  }],
}, {
 
  timestamps: true
})

const alumnoResSchema = new Schema({
  nombre: {
    type: String
  },
  telefono: {
    type: Number
  },
  visita: {
    type: Date
  },
  empresa: {
    type: String
  },
  alumnoid: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'alumno'
  }
}, {
  timestamps: true,
  toJSON: {
    virtuals: true,
    transform: (obj, ret) => { delete ret._id }
  }
})