Modelling for friends schema in mongoose?

How do I model my mongoose schema to get these three buttons when I am on the other users profile?

  1. Add Friend
  2. Requested
  3. Friends

My users schema

const schema = new Mongoose.Schema({
  firstName: { type: String, default: '', trim: true },
  lastName: { type: String, default: '', trim: true },
}, { timestamps: true })

I could not find the correct modelling for this... And also please suggest the aggregation after modelling...