Added MemberProductEvent model & relations

refs https://github.com/TryGhost/Team/issues/873

We need a relation between members and their product events so that we
can pull out the events for a particular member to generate the start
date of their comped access to a product.

core/server/models/index.js

@@ -38,6 +38,7 @@ const models = [
     'member-email-change-event',
     'member-payment-event',
     'member-status-event',
+    'member-product-event',
     'posts-meta',
     'member-stripe-customer',
     'stripe-customer-subscription',

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

@@ -0,0 +1,41 @@
+const errors = require('@tryghost/errors');
+const tpl = require('@tryghost/tpl');
+const ghostBookshelf = require('./base');
+
+const messages = {
+    cannotPerformAction: 'Cannot {action} MemberProductEvent'
+};
+
+const MemberProductEvent = ghostBookshelf.Model.extend({
+    tableName: 'members_product_events',
+
+    member() {
+        return this.belongsTo('Member', 'member_id', 'id');
+    },
+
+    product() {
+        return this.belongsTo('Product', 'product_id', 'id');
+    }
+
+}, {
+    async edit() {
+        throw new errors.IncorrectUsageError(
+            tpl(messages.cannotPerformAction, 'edit')
+        );
+    },
+
+    async destroy() {
+        throw new errors.IncorrectUsageError(
+            tpl(messages.cannotPerformAction, 'destroy')
+        );
+    }
+});
+
+const MemberProductEvents = ghostBookshelf.Collection.extend({
+    model: MemberProductEvent
+});
+
+module.exports = {
+    MemberProductEvent: ghostBookshelf.model('MemberProductEvent', MemberProductEvent),
+    MemberProductEvents: ghostBookshelf.collection('MemberProductEvents', MemberProductEvents)
+};

core/server/models/member.js

@@ -78,6 +78,11 @@ const Member = ghostBookshelf.Model.extend({
         email_recipients: 'email_recipients'
     },
 
+    productEvents() {
+        return this.hasMany('MemberProductEvent', 'member_id', 'id')
+            .query('orderBy', 'created_at', 'DESC');
+    },
+
     products() {
         return this.belongsToMany('Product', 'members_products', 'member_id', 'product_id')
             .withPivot('sort_order')