constructor({db, settingsCache, isSQLite}) {
        this._db = db;
        this._settingsCache = settingsCache;
        this._isSQLite = isSQLite;
    }
@param {Object} config
@param {Object} config.db - an instance holding knex connection to the database
@param {Object} config.settingsCache - an instance of the Ghost Settings Cache
@param {Boolean} config.isSQLite - flag identifying if storage is connected to SQLite