Typescript CreationAttributes are always being marked as optional with strictNullChecks disabled

No repository files or tests are identified. Start by reproducing the supplied Sequelize model example with TypeScript 4.5.4 and strictNullChecks disabled, then trace the creation-attribute typings involved in Model creation. Done means omitting required name or height produces a TypeScript error while the optional id remains allowed.

Issue Creation Checklist

• I have read the contribution guidelines

Bug Description

Typescript CreationAttributes are being marked as optional regardless of actually marking them as so. When creating a model typescript does not complain about some required parameters that are missing because of this.

Example

import { DataTypes, Model, Optional, Sequelize } from "sequelize"

interface Attributes {
    id: string
    name: string
    height: number
}

type CreationAttributes = Optional<Attributes, "id">

export default class Person extends Model<Attributes, CreationAttributes> implements Attributes {
    public id!: string
    public name!: string
    public height!: number

    public static initialize(sequelize: Sequelize) {
        this.init({
            id: {
                type: DataTypes.UUID,
                defaultValue: DataTypes.UUIDV4,
                field: "ID",
                primaryKey: true,
                allowNull: false,
            },
            name: {
                type: DataTypes.STRING,
                field: "Name",
                allowNull: false,
            },
            height: {
                type: DataTypes.NUMBER,
                field: "Height",
                allowNull: false,
            }
        }, {
            sequelize: sequelize,
            tableName: "Person"
        })
    }
}

What do you expect to happen?

It should throw a typescript error if Person.name and Person.height are not provided when creating a Person.

What is actually happening?

Typescript thinks name is optional even though it's being marked as required.

Typescript does not complain when required fields are omitted.

Environment

• Sequelize version: sequelize@6.18.0
• Node.js version: v14.19.1
• ITypeScript version: typescript@4.5.4

Would you be willing to resolve this issue by submitting a Pull Request?

• No, I don't have the time, although I believe I could do it if I had the time...