Radio button option IDs are not unique

[SpiraMira]

I'm submitting a ... (check one with "x")

[x ] bug report => search github for a similar issue or PR before submitting
[ ] feature request
[ ] support request

Current behavior

• A simple Radio button generates options with non-unique ids (per below in Chrome developer console)

[DOM] Found 2 elements with non-unique id #formly_2_radio_title_0: (More info: https://goo.gl/9p2vKq) <input class=​"custom-control-input ng-untouched ng-pristine ng-valid" type=​"radio" ng-reflect-name=​"formly_2_radio_title_0" ng-reflect-value=​"mr" ng-reflect-form=​"[object Object]​" id=​"formly_2_radio_title_0" aria-describedby=​"formly_2_radio_title_0-message" ng-reflect-field=​"[object Object]​" ng-reflect-form-control=​"[object Object]​">​ <input class=​"custom-control-input ng-untouched ng-pristine ng-valid" type=​"radio" ng-reflect-name=​"formly_2_radio_title_0" ng-reflect-value=​"mrs" ng-reflect-form=​"[object Object]​" id=​"formly_2_radio_title_0" aria-describedby=​"formly_2_radio_title_0-message" ng-reflect-field=​"[object Object]​" ng-reflect-form-control=​"[object Object]​">​

Here is an excerpt of the field config:

``
fields: FormlyFieldConfig[] = [
{
fieldGroupClassName: 'row',
className: 'col-12',
fieldGroup: [{
className: 'col-12',
type: 'radio',
key: 'title',
// formControl: new FormControl('mrs'),
templateOptions: {
options: [{
key: 'mr',
value: 'Mr.',
}, {
key: 'mrs',
value: 'Mrs',
}],
label: 'Title',
description: 'Select a title that suits your description',
}
}, {

``
Expected behavior

For the component to generate a unique Id per radio button option.

Minimal reproduction of the problem with instructions

adda radio button
What is the motivation / use case for changing the behavior?

bug
Please tell us about your environment:

macOS Sierra
Visual Studio Code
Angular 5+
node v9.2.1
npm v5.5.1

• Angular version: 2.0.X

yes

• Browser: [all | Chrome 63 | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

Chrome 63

• Language: [all | TypeScript 2.6.2 | ES6/7 | ES5]
• Node (for AoT issues): node --version = 9.2.1