exports.financialsConfig = functions
// .runWith(runtimeOpts)
.https.onCall((data) => {
    return db.collection('financials').get()
    .limit(25)
    .then((qs: QuerySnapshot) => {
      qs.forEach((fDoc: QueryDocumentSnapshot) => {
        // A way to filter out the unwanted properties and keep desired ones.
        // See https://codeburst.io/use-es2015-object-rest-operator-to-omit-properties-38a3ecffe90
        const {childFirstName, childLastName, fatherEmail, motherEmail, grade, ...keep} = fDoc.data();
        return db.collection('students').doc(fDoc.id).collection('financials').doc(fDoc.id).set(keep)
          .then(()=> {
            // Go to the top-level 'financials' collection and
            // get all the docs from each subcollection with each financial doc.

            // Cloud function for each collection.
            const collections = ['extendedCareCharges',
                                  'extendedCarePayments',
                                  'lunchCharges',
                                  'lunchPayments',
                                  'miscCharges',
                                  'miscPayments',
                                  'tuitionCharges',
                                  'tuitionPayments'];
            collections.forEach(collection => {
              return db.collection('financials').doc(fDoc.id).collection(collection)
              .get()
              .then((qss: QuerySnapshot) => {
                  console.log(`MD: qss`, qss);