use new url parser mongoose code example

Example 1: DeprecationWarning: current Server Discovery and Monitoring engine is deprecated,

mongoose.connect("paste db link", {useUnifiedTopology: true, useNewUrlParser: true, useCreateIndex: true });

Example 2: https://mongoosejs.com/docs/deprecations.html#findandmodify

// Make Mongoose use `findOneAndUpdate()`. Note that this option is `true`
// by default, you need to set it to false.
mongoose.set('useFindAndModify', false);