Javascript – Cloud Function in Firebase to check the age of users

I am writing an app in Flutter with a Firebase Backend. My App needs to check if a user turnt 18, and if they did it should make their attribute "hasAgreedToTerms" to false because I want them to re-agree to the Terms and Conditions after they turn 18. I have looked around online and asked ChatGPT and it seems like I need to add a Cloud Function to Firebase that checks their age. I have tried implementing a function but I do not have any experience with JS, therefore I have trouble writing the function. Additionally, when I try to deploy my function, an error occurs.

const functions = require("firebase-functions");
const admin = require("firebase-admin");
admin.initializeApp();

exports.checkUserAgeAndUpdateTerms = functions.firestore
    .document("users/{userId}")
    .onUpdate(async (change, context) => {
      const userId = context.params.userId;
      const newData = change.after.data(); // Get the updated data

      // Check if the birthdate exists
      if (!newData.birthdate) {
        console.log("No birthdate found for user:", userId);
        return null;
      }

      const birthdate = new Date(newData.birthdate);
      const age = calculateAge(birthdate);

      // Check if the user is 18 or older
      if (age >= 18) {
        // Update the 'hasAgreedToTerms' field to false
        await admin.firestore().collection("users").doc(userId).update({
          hasAgreedToTerms: false,
        });
        console.log("User ${userId} turnt 18. Updated hAtT to false.");
      }

      return null;
    });

/**
 * Function
 * @param {Date} birthdate
 * @return {boolean} Description of the return value
 */
function calculateAge(birthdate) {
  const today = new Date();
  let age = today.getFullYear() - birthdate.getFullYear();
  const monthDiff = today.getMonth() - birthdate.getMonth();
  if (monthDiff < 0 || (monthDiff === 0 &&
  today.getDate() < birthdate.getDate())) {
    age--;
  }
  return age;
}

I tried updating my firebase-functions version and using 2nd gen cloud functions, but I have no experience and could not write something working.picture of the error