Added fallback sending domain option for email batches

closes
[GVA-587](https://linear.app/ghost/issue/GVA-587/create-a-migration-for-the-email-batches-table-to-say-whether-its-sent)

We need to know whether an email batch should be sent from the fallback
domain or the primary configured domain.

See [spike PR](#25303) for our
test implementation.

Author: sam-lord

ghost/core/core/server/data/migrations/versions/6.7/2025-11-03-15-18-04-add-email-batch-fallback-domain.js

@@ -0,0 +1,7 @@
+const {createAddColumnMigration} = require('../../utils');
+
+module.exports = createAddColumnMigration('email_batches', 'fallback_sending_domain', {
+    type: 'boolean',
+    nullable: false,
+    defaultTo: false
+});

ghost/core/core/server/data/schema/schema.js

@@ -867,6 +867,7 @@ module.exports = {
         id: {type: 'string', maxlength: 24, nullable: false, primary: true},
         email_id: {type: 'string', maxlength: 24, nullable: false, references: 'emails.id'},
         provider_id: {type: 'string', maxlength: 255, nullable: true},
+        fallback_sending_domain: {type: 'boolean', nullable: false, defaultTo: false},
         status: {
             type: 'string',
             maxlength: 50,

ghost/core/test/unit/server/data/schema/integrity.test.js

@@ -35,7 +35,7 @@ const validateRouteSettings = require('../../../../../core/server/services/route
  */
 describe('DB version integrity', function () {
     // Only these variables should need updating
-    const currentSchemaHash = '5d90909b1b8232b45f0174dfa720a051';
+    const currentSchemaHash = '4e68fd06f63aab5fef99dddd8dc866bb';
     const currentFixturesHash = '0877727032b8beddbaedc086a8acf1a2';
     const currentSettingsHash = 'bb8be7d83407f2b4fa2ad68c19610579';
     const currentRoutesHash = '3d180d52c663d173a6be791ef411ed01';