Refactored default settings population to reduce unnecessary DB queries

refs https://github.com/TryGhost/Toolbox/issues/202

- this code suffers from two problems:
  - when we don't have any new settings to insert, we still end up
    fetching the columnInfo and owner info, even though we only need
    them if we're inserting data. This results in 3 extra queries upon
    boot
  - secondly, we insert every setting with a separate query - MySQL and
    SQLite both support batch inserts and knex has a utility to help us
    that I've [used
    before](38821c5242).
    With 95 settings at the time of writing, this adds 94 extra queries
    during the DB init
- this commit refactors the code so that we only fetch the columnInfo and
  owner data if we've got new settings to insert, and batches the
  inserts using knex's batchInsert util
- this query results in ~95 less queries during DB init and saves a
  couple of queries during boot

core/server/models/settings.js

@@ -260,62 +260,60 @@ Settings = ghostBookshelf.Model.extend({
         await ghostBookshelf.knex.destroy();
         await ghostBookshelf.knex.initialize();
 
-        // fetch available columns to avoid populating columns not yet created by migrations
-        const columnInfo = await ghostBookshelf.knex.table('settings').columnInfo();
-        const columns = Object.keys(columnInfo);
+        const allSettings = await this.findAll(options);
 
-        // fetch other data that is used when inserting new settings
-        const date = ghostBookshelf.knex.raw('CURRENT_TIMESTAMP');
-        let owner;
-        try {
-            owner = await ghostBookshelf.model('User').getOwnerUser();
-        } catch (e) {
-            // in some tests the owner is deleted and not recreated before setup
-            if (e.errorType === 'NotFoundError') {
-                owner = {id: 1};
-            } else {
-                throw e;
+        const usedKeys = allSettings.models.map(function mapper(setting) {
+            return setting.get('key');
+        });
+
+        const settingsToInsert = [];
+
+        _.each(getDefaultSettings(), function forEachDefault(defaultSetting, defaultSettingKey) {
+            const isMissingFromDB = usedKeys.indexOf(defaultSettingKey) === -1;
+            if (isMissingFromDB) {
+                defaultSetting.value = defaultSetting.getDefaultValue();
+                settingsToInsert.push(defaultSetting);
             }
+        });
+
+        if (settingsToInsert.length > 0) {
+            // fetch available columns to avoid populating columns not yet created by migrations
+            const columnInfo = await ghostBookshelf.knex.table('settings').columnInfo();
+            const columns = Object.keys(columnInfo);
+
+            // fetch other data that is used when inserting new settings
+            const date = ghostBookshelf.knex.raw('CURRENT_TIMESTAMP');
+            let owner;
+            try {
+                owner = await ghostBookshelf.model('User').getOwnerUser();
+            } catch (e) {
+                // in some tests the owner is deleted and not recreated before setup
+                if (e.errorType === 'NotFoundError') {
+                    owner = {id: 1};
+                } else {
+                    throw e;
+                }
+            }
+
+            const settingsDataToInsert = settingsToInsert.map((setting) => {
+                const settingValues = Object.assign({}, setting, {
+                    id: ObjectID().toHexString(),
+                    created_at: date,
+                    created_by: owner.id,
+                    updated_at: date,
+                    updated_by: owner.id
+                });
+
+                return _.pick(settingValues, columns);
+            });
+
+            await ghostBookshelf.knex
+                .batchInsert('settings', settingsDataToInsert);
+
+            return self.findAll(options);
         }
 
-        return this
-            .findAll(options)
-            .then(function checkAllSettings(allSettings) {
-                const usedKeys = allSettings.models.map(function mapper(setting) {
-                    return setting.get('key');
-                });
-
-                const insertOperations = [];
-
-                _.each(getDefaultSettings(), function forEachDefault(defaultSetting, defaultSettingKey) {
-                    const isMissingFromDB = usedKeys.indexOf(defaultSettingKey) === -1;
-                    if (isMissingFromDB) {
-                        defaultSetting.value = defaultSetting.getDefaultValue();
-
-                        const settingValues = Object.assign({}, defaultSetting, {
-                            id: ObjectID().toHexString(),
-                            created_at: date,
-                            created_by: owner.id,
-                            updated_at: date,
-                            updated_by: owner.id
-                        });
-
-                        insertOperations.push(
-                            ghostBookshelf.knex
-                                .table('settings')
-                                .insert(_.pick(settingValues, columns))
-                        );
-                    }
-                });
-
-                if (insertOperations.length > 0) {
-                    return Promise.all(insertOperations).then(function fetchAllToReturn() {
-                        return self.findAll(options);
-                    });
-                }
-
-                return allSettings;
-            });
+        return allSettings;
     },
 
     permissible: function permissible(modelId, action, context, unsafeAttrs, loadedPermissions, hasUserPermission, hasApiKeyPermission) {