feat(carousel-native): association

[Andries-Smit]

The carousel widget is limited to static use cases. On the initial render, the first item is always shown. When the user changes an active item in the carousel, there is no way that the context can be aware of the active item. There is no way to change the active item in the carousel by any logic.

Use cases:

• Open an item in the middle of the carousel.
• Have a button outside of the carousel that applies to the contents of the carousel.
• Have buttons control the current state of the carousel.
• Fire an event (for example, nanoflow) when the carousel active item changes.

Solution: carousel as reference selector:

• Add an association of the carousel's context to the carousel's content item. This function is similar to the reference selector, except the carousel always selects one item.
• Add an "On change" event on the association.
• Have a way to control if the active items change with/without animation. (No animation, allowing the carousel to change before an overlaying page is closed.)
  See the animation below...

This requires some defined states of what happens when:

Action	Reference select	Carousel	Carousel with association
First render, No association set	no selection	Show first index	Set first as reference
Empty data source, add data	no selection	Show first index	Set first as reference
Delete item, after current selected	no change	Persist selected index	Persist current selection
Delete current selected	Association set to empty	Index persist, item after is selected	Move to index 0
Delete item, before current	No change	Index persist, item after previous selected	Persist selected, change index
All items removed	No selection	Carousel not visible	Association set to empty
Add before current selected	No change	Persist selected index, change active	Persist current selection, change index