// User Schema
const UserSchema = new Schema({

    // PERSONAL USER INFO
    username: {
        type: String,
        required: true,
        index: true,
        unique: true,
    },
    email: {
        type: String,
        required: true,
        index: true,
        unique: true
    },
    password: {
        type: String,
        required: true,
    },
    ....
});