NgbRadioGroup keyboard navigation shouldn't go to the next radio group

[jnizet]

Bug description:

When there are several groups of radio buttons (using ngbRadioGroup) on the same page, navigating with the keyboard from radio to radio, using arrow keys, should keep the focus in the same group and cycle. Instead, the focus jumps from the last radio of the group to the first radio of the next group, which is quite surprising.

The issue can be fixed by specifying a name on the input elements of the group, but

• the ng-bootstrap demo doesn't do that; so if it's needed, the demo should be fixed
• it feels redundant to specify a name on the inputs when we have already specified one on the ngbRadioGroup. Maybe the directive should add the name attribute to the inputs.

Link to minimally-working plunker that reproduces the issue:

http://plnkr.co/edit/QQyl35agwv4DM8FB7DZD?p=preview

Version of Angular, ng-bootstrap, and Bootstrap:

Angular: 4.3.1

ng-bootstrap: 1.0.0-alpha.29

Bootstrap: 4.0.0-alpha.6

[pkozlowski-opensource]

Good catch @jnizet !

Now that we've got a directive specifically targeting input elements (https://ng-bootstrap.github.io/#/components/buttons/api#NgbRadio) we could indeed generate names.

How about this: we add a new name @Input() and if none is provided we generate names (similarly to what we do with ids in several places). Fancy a PR?

[jnizet]

I'll try doing that.