Backfilled offer redemptions for subscriptions with missing redemptions

ref https://linear.app/tryghost/issue/ENG-1440/backfill-offer-redemption-data-with-a-migration
ref bf895e6

There was a bug that caused offer redemptions to not be recorded in the database for some subscriptions that were created with an offer. The bug was fixed in the references commit above.

This commit backfills the missing redemptions, based on the subscriptions that have an `offer_id` but no corresponding offer redemptions.

ghost/core/core/server/data/migrations/versions/5.89/2024-07-30-19-51-06-backfill-offer-redemptions.js

@@ -0,0 +1,64 @@
+// For information on writing migrations, see https://www.notion.so/ghost/Database-migrations-eb5b78c435d741d2b34a582d57c24253
+
+const logging = require('@tryghost/logging');
+const DatabaseInfo = require('@tryghost/database-info');
+const {default: ObjectID} = require('bson-objectid');
+
+// For DML - data changes
+const {createTransactionalMigration} = require('../../utils');
+
+module.exports = createTransactionalMigration(
+    async function up(knex) {
+        // Backfill missing offer redemptions
+        try {
+            // Select all subscriptions that have an `offer_id` but don't have a matching row in the `offer_redemptions` table
+            logging.info('Selecting subscriptions with missing offer redemptions');
+            const result = await knex.raw(`
+                SELECT
+                    mscs.id AS subscription_id,
+                    mscs.offer_id,
+                    mscs.start_date AS created_at,
+                    m.id AS member_id
+                FROM
+                    members_stripe_customers_subscriptions mscs
+                        LEFT JOIN
+                    offer_redemptions r ON r.subscription_id = mscs.id
+                        INNER JOIN 
+                    members_stripe_customers msc ON mscs.customer_id = msc.customer_id
+                        INNER JOIN
+                    members m ON msc.member_id = m.id
+                WHERE
+                    mscs.offer_id IS NOT NULL and r.id IS NULL;
+            `);
+
+            // knex.raw() returns a different result depending on the database. We need to handle either case
+            let rows = [];
+            if (DatabaseInfo.isSQLite(knex)) {
+                rows = result;
+            } else {
+                rows = result[0];
+            }
+
+            // Do the backfil
+            if (rows && rows.length > 0) {
+                logging.info(`Backfilling ${rows.length} offer redemptions`);
+                // Generate IDs for each row
+                const offerRedemptions = rows.map((row) => {
+                    return {
+                        id: new ObjectID().toHexString(),
+                        ...row
+                    };
+                });
+                // Batch insert rows into the offer_redemptions table
+                await knex.batchInsert('offer_redemptions', offerRedemptions, 1000);
+            } else {
+                logging.info('No offer redemptions to backfill');
+            }
+        } catch (error) {
+            logging.error(`Error backfilling offer redemptions: ${error.message}`);
+        }
+    },
+    async function down() {
+        // We don't want to un-backfill data, so do nothing here.
+    }
+);