Added mail provider api key setting migration

no issue

core/server/data/migrations/versions/3.1/05-add-mail-api-key-to-members-settings.js

@@ -0,0 +1,55 @@
+const _ = require('lodash');
+const Promise = require('bluebird');
+const common = require('../../../../lib/common');
+
+module.exports.config = {
+    transaction: true
+};
+
+module.exports.up = (options) => {
+    let localOptions = _.merge({
+        context: {internal: true}
+    }, options);
+    const settingsKey = 'members_subscription_settings';
+    return localOptions
+        .transacting('settings')
+        .then((response) => {
+            if (!response) {
+                common.logging.warn('Cannot find settings.');
+                return;
+            }
+            let subscriptionSettingsEntry = response.find((entry) => {
+                return entry.key === settingsKey;
+            });
+
+            if (!subscriptionSettingsEntry) {
+                common.logging.warn('Cannot find members subscription settings.');
+                return;
+            }
+            let subscriptionSettings = JSON.parse(subscriptionSettingsEntry.value);
+
+            let hasMailgunApiKeyProperty = Object.prototype.hasOwnProperty.call(subscriptionSettings, 'mailgunApiKey');
+
+            if (!hasMailgunApiKeyProperty) {
+                subscriptionSettings.mailgunApiKey = '';
+                common.logging.info('Adding mail provider API key to members settings');
+            } else {
+                common.logging.warn('Mail provider API key setting already exists in members settings.');
+            }
+
+            return localOptions
+                .transacting('settings')
+                .where('key', settingsKey)
+                .update({
+                    value: JSON.stringify(subscriptionSettings)
+                });
+        });
+};
+
+// `up` only runs in order to normalize new member subscription settings which was added
+// no need for down migration as its non-breaking up migration for future versions only
+module.exports.down = () => Promise.resolve();
+
+module.exports.config = {
+    transaction: true
+};