(change) Make Notifier interface publicly implementable

[shezadkhan137]

Motivation

Make the Notifier interface publicly implementable.

Hi, thanks for making this library! I would like to output feature flag changes to our internal Grafana via the Annotations API.

The current Webhook notifier doesn't satisfy our need, as we would like to format the text for the annotation based on the diff. We could do this via an intermediate web server that translates the Webhook notifier payload for Grafana, but it would be nice to do it without the intermediate server.

Requirements

Ideally, go-feature-flag should allow the notifier interface to be implemented publically and support custom notifiers passed in completely via the Config. Currently is not possible because the GetNotifier interface returns the internal Notifier interface. Also, the Notifier interface accepts an internal model.DiffCache struct.

Would it be possible to make these part of the public API? I think it may be just a matter of taking it out of the internal package and into a public notifier package?

I'm more than willing to put a PR in, if you are okay with making it public. Thanks!

[urso]

Other interfaces like Exporter face the same issue. Maybe it would make sense to rename internal to pkg or move some more packages from internal one level up?

[thomaspoignant]

@shezadkhan137 Sorry I just see your issue today.
I will check what I can do to change the way the notifier works to make them public.

And feel free to open a PR for that.

@urso thanks for the idea I will look at them.

[thomaspoignant]

Other interfaces like Exporter face the same issue. Maybe it would make sense to rename internal to pkg or move some more packages from internal one level up?

I have exposed FeatureEvent publicly for the Exporter, now it should work. See #225.

[thomaspoignant]

I am really sorry for the delay @shezadkhan137, I have released a v0.20.0 version that allows creating custom notifiers.
I have added an example of how to do that in the documentation.

Feel free to give me any feedback if it works well for you.

[shezadkhan137]

Wow, thanks so much @thomaspoignant. Will give it a go and let you know :-)

[urso]

I have exposed FeatureEvent publicly for the Exporter, now it should work. See #225.

Thanks!