Using Custom Email Templates with Firebase Authentication

functions.js

exports.verifyEmail = functions.auth.user().onCreate(async(user) => {
    try {
        const token = crypto.randomBytes(48);
        await admin.firestore().collection("users").doc(user.uid).set({
            name: user.displayName,
        });
        await admin.firestore().collection("activationTokens").doc(user.uid).set({
            token: token.toString('hex'),
            expires: Date.now() + ( 3600 * 1000 * 24)
        });

        const email = new Email ({
            message: {
                from: "noreply@domain.com",
                subject: "Activate your Account!",
                to: user.email
            },
            send: true,
            transport: {
                host: "smtp.mailtrap.io",
                port: 2525,
                auth: {
                    user: "abc",
                    pass: "123"
                }
            },
            views: {
                options: {
                    extension: 'ejs'
                }
            }
        });

        return email.send({
            template: 'activateAccount',
            locals: {
                name: user.displayName,
                url: data.url
            },
        });

    } catch (e) {
        console.log(e)
    }
});

register.js

function handleSubmit(form) {
  try {
    await firebase.auth().createUserWithEmailAndPassword(form.email, form.password);
  } catch (e) {
    console.log(e);    
  }
}