feat: Set Unleash changed flags on change event.

[RafeArnold]

This PR

• adds the flags that have been changed to the configuration change event for the Unleash provider.

Notes

This addition makes checking which flags have updated trivial for the end-user.

[liran2000]

hi @RafeArnold thanks for the changes, looks good.
can you please add some background, on how did you come up with this need, where is it used etc' ?

[RafeArnold]

hi @RafeArnold thanks for the changes, looks good. can you please add some background, on how did you come up with this need, where is it used etc' ?

The background for this change is that being able to see which flags have actually been updated when a ProviderConfigurationChanged event is emitted is really useful at preventing unnecessary work for the receiver of the event. If a event handler is only interesting in a single flag, or a subset of flags, they can easily query the received event to see if the flags they care about have changed.

I've realised that my implementation isn't actually doing what I intended, since the ToggleResponse will contain all the feature toggles available, not just the updated ones. I guess the subscriber wrapper would require a cache of the flag keys that it could compare and update with the flags that were retrieved from the Unleash API. I'll have another crack at it and see what I can produce.

[RafeArnold]

Having thought about it further, to implement my intention, I believe the subscriber wrapper would need to keep its own cache of all the flags, which feels like a huge waste of resources. If this is the case, having the event receivers perform the checks themselves seems like the best option. Feel free to close this PR, unless a better solution can be thought of.

[liran2000]

What does toggleResponse.getToggleCollection().getFeatures() contain ?
Only changed features ?
Any documentation reference from Unleash ?

[RafeArnold]

Yeah, unfortunately, as per my other comment, it contains all the feature toggles available from the Unleash API, not just the changed ones, so this implementation doesn't work as intended.