Backfilled missing offer redemptions (#20647)

ref
https://linear.app/tryghost/issue/ENG-1440/backfill-offer-redemption-data-with-a-migration
    
There was a bug that caused offer redemptions to not be recorded in the
database for some subscriptions that were created with an offer.
However, we still have the `offer_id` attached to the subscriptions, so
we are able to backfill the missing redemptions. The bug was fixed in
bf895e6e99
    
This commit only contains a migration, which queries for subscriptions
that have an `offer_id` but do not have any offer redemptions recorded,
and adds any missing redemptions to the `offer_redemptions` table.

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.
+    }
+);