I have 2 collections in my Firestore, 'students' and 'student_history'. Every time a document is created or updated in 'students', I want to fetch it using a cloud function, add a field called {"Created At" : "timestamp"} or {"Updated At" : "timestamp"} to the document and write this new document into 'student_history'.

Here are the firebase cloud functions that I have managed to write for the same :

const functions = require("firebase-functions");
const admin = require("firebase-admin");
admin.initializeApp();
const db = admin.firestore();
exports.onUserCreate = functions.firestore.
    document("students/{student_id}").onCreate(
        async (snap, context) => {
          const values = snap.data(); //line 8
          console.log(values);
          console.log(typeof values);
          await db.collection("student_history").add(values);
        });
exports.onUserUpdate = functions.firestore.
    document("students/{student_id}").onUpdate(
        async (snap, context) => {
          const values = snap.after.data();
          console.log(values);
          console.log(typeof values);
          await db.collection("student_history").add(values);
        });

Ideally, I want to be able to append a field like {"Created At" : "timestamp"} to 'values' before adding it to 'student_history'. What would be the correct way to achieve this or is there a better/different solution for the entire scenario? Thank you.