🏗 Migrated subscribers data to members (#11152)

no issue 

- Populates members table with existing subscribers. Only takes into account columns we know already exist and need to be copied i.e `name`/`email`

core/server/data/migrations/versions/3.0/12-populate-members-table-from-subscribers.js

@@ -0,0 +1,53 @@
+const ObjectId = require('bson-objectid');
+const _ = require('lodash');
+const models = require('../../../../models');
+const common = require('../../../../lib/common');
+
+module.exports.config = {
+    transaction: true,
+    irreversible: true
+};
+
+module.exports.up = (options) => {
+    const localOptions = _.merge({
+        context: {internal: true},
+        migrating: true
+    }, options);
+
+    const memberAttrs = [
+        'name',
+        'email',
+        'created_at',
+        'created_by',
+        'updated_at',
+        'updated_by'
+    ];
+
+    return models.Subscribers
+        .forge()
+        .fetch(localOptions)
+        .then(({models: subscribers}) => {
+            if (subscribers.length > 0) {
+                common.logging.info(`Adding ${subscribers.length} entries to members`);
+
+                let members = _.map(subscribers, (subscriber) => {
+                    let member = memberAttrs.reduce(function (obj, prop) {
+                        return Object.assign(obj, {
+                            [prop]: subscriber.get(prop)
+                        });
+                    }, {});
+                    member.id = ObjectId.generate();
+
+                    return member;
+                });
+                return localOptions.transacting('members').insert(members);
+            } else {
+                common.logging.info('Skipping populating members table: found 0 subscribers');
+                return Promise.resolve();
+            }
+        });
+};
+
+module.exports.down = () => {
+    return Promise.reject();
+};