Included products when exporting member csv

refs https://github.com/TryGhost/Team/issues/765

Since Members can be given complimentary access to one of many products,
we must include which products a member has access to when exporting
from Ghost. This will allow us to reimport without losing information.

core/server/api/canary/members.js

@@ -448,6 +448,9 @@ module.exports = {
         validation: {},
         async query(frame) {
             frame.options.withRelated = ['labels', 'stripeSubscriptions', 'stripeSubscriptions.customer'];
+            if (labsService.isSet('multipleProducts')) {
+                frame.options.withRelated.push('products');
+            }
             const page = await membersService.api.members.list(frame.options);
 
             return page;