_resolveContextSource(context) {
        let source;

        if (context.import || context.importer) {
            source = 'import';
        } else if (context.internal) {
            source = 'system';
        } else if (context.api_key) {
            source = 'api';
        } else if (context.user) {
            source = 'admin';
        } else {
            source = 'member';
        }

        return source;
    }
Maps the framework context to source string
@param {Object} context instance of ghost framework context object
@returns {'import' | 'system' | 'api' | 'admin' | 'member'}
@private