src/vs/platform/telemetry/common/telemetryUtils.ts/flatKeys
function flatKeys(result: string[], prefix: string, value: { [key: string]: any } | undefined): void {
	if (value && typeof value === 'object' && !Array.isArray(value)) {
		Object.keys(value)
			.forEach(key => flatKeys(result, prefix ? `${prefix}.${key}` : key, value[key]));
	} else {
		result.push(prefix);
	}
}