habitica-self-host/website/server/models/pushDevice.js

import mongoose from 'mongoose';
import baseModel from '../libs/baseModel';

const { Schema } = mongoose;

export const schema = new Schema({
  regId: { $type: String, required: true },
  type: { $type: String, required: true, enum: ['ios', 'android'] },
}, {
  strict: true,
  minimize: false, // So empty objects are returned
  _id: false,
  typeKey: '$type', // So that we can use a field named `type`
});

schema.plugin(baseModel, {
  noSet: ['_id', 'regId'],
  timestamps: true,
  _id: false,
});

export const model = mongoose.model('PushDevice', schema);