Populated email table source with existing html data

refs https://github.com/TryGhost/Team/issues/2280

- updates `source` value for all existing rows to contain `html` data for future compatibility with new columns

ghost/core/core/server/data/migrations/versions/5.24/2022-11-21-15-03-populate-source-column-with-html-for-emails.js

@@ -0,0 +1,19 @@
+const logging = require('@tryghost/logging');
+const {createTransactionalMigration} = require('../../utils');
+
+module.exports = createTransactionalMigration(
+    async function up(knex) {
+        logging.info('Populating source from html in emails table');
+
+        const affectedRows = await knex('emails')
+            .update({
+                source: knex.ref('html')
+            });
+
+        logging.info(`Updated ${affectedRows} rows with source html data`);
+    },
+
+    async function down() {
+        // no-op: we don't want to remove the data
+    }
+);