How to model types in Typescript and Mongoose

ts-models.ts

/*
Lets have type models in Typescript and keep it simple
- borrows from https://brianflove.com/2016/10/04/typescript-declaring-mongoose-schema-model/
- validation is useful when parsing data from external APIs
- avoids typegoose, class-validator, class-transform in favour of stable features
*/

import * as mongoose from 'mongoose';
import { Document, Model, Schema, model } from "mongoose";
import jointz, { ExtractResultType } from "jointz";

const UserValidator = jointz.object({
  email: jointz.string(),
  firstName: jointz.string(),
  lastName: jointz.string(),
})

type UserType = ExtractResultType<typeof UserValidator>;

interface UserModel extends UserType, Document {
}

const userSchema = new Schema({
  createdAt: {
    type: Date,
    defaults: new Date()
  },
  email: String,
  firstName: String,
  lastName: String,
})

const User: Model<UserModel> = model<UserModel>('User', userSchema);

(async () => {
  await mongoose.connect('mongodb://localhost:27017/ts-models', {
    useNewUrlParser: true,
    useUnifiedTopology: true
  });

  const props: UserType = { email: 'test@me.com', firstName: 'First', lastName: 'Last' };
  const user = new User(props);
  await user.save();

  const invalid = { fullName: 'First Last' };
  if(!UserValidator.isValid(invalid)) {
    console.warn('Invalid user props')
  }
})();