Added skeleton MemberSubscribeEvent model

refs https://github.com/TryGhost/Ghost/issues/12602

Member Events in general are read-only after they've been created, so
we've explicitly disallowed destroying and editing via the model

core/server/models/index.js

@@ -28,6 +28,7 @@ const models = [
     'api-key',
     'mobiledoc-revision',
     'member',
+    'member-subscribe-event',
     'posts-meta',
     'member-stripe-customer',
     'stripe-customer-subscription',

core/server/models/member-subscribe-event.js

@@ -0,0 +1,20 @@
+const ghostBookshelf = require('./base');
+
+const MemberSubscribeEvent = ghostBookshelf.Model.extend({tableName: 'members_subscribe_events'}, {
+    async edit() {
+        throw new errors.IncorrectUsageError('Cannot edit MemberSubscribeEvent');
+    },
+
+    async destroy() {
+        throw new errors.IncorrectUsageError('Cannot destroy MemberSubscribeEvent');
+    }
+});
+
+const MemberSubscribeEvents = ghostBookshelf.Collection.extend({
+    model: MemberSubscribeEvent
+});
+
+module.exports = {
+    MemberSubscribeEvent: ghostBookshelf.model('MemberSubscribeEvent', MemberSubscribeEvent),
+    MemberSubscribeEvents: ghostBookshelf.collection('MemberSubscribeEvents', MemberSubscribeEvents)
+};