Move retriever / notifier / exporter on their own packages.

[thomaspoignant]

Description

⚠️ Breaking changes ⚠️

This version change the way to do your SDK initialization in particular when it comes to notifier, provider and exporter.

Why are we doing this breaking changes?

This change is needed because we are adding more and more retriever / exporter and notifier, and with that we are also adding more dependencies to the project.
And since all the dependencies are in the same package we were increasing the size of your build even if you were not using the new providers.

The best example is when we introduce the kubernetes provider, it has added ~20Mo in your application because the client-go from kubernetes is huge.

What did we change?

We have moved all retriever / exporter and notifier in a dedicated package for each of them.
With this new organisation when building your app we will use only the dependencies related to your configuration.

We also change the way to deal with the notifiers to align it with the way it work for other extensions.

How to migrate?

Edit your init function of go-feature-flag and replace your retriever, exporter, notifier following this.

Retrievers

ffclient.FileRetriever          ->      fileretriever.Retriever
ffclient.GithubRetriever        ->      gcstorageretriever.Retriever
ffclient.GithubRetriever        ->      githubretriever.Retriever
ffclient.HTTPRetriever          ->      httpretriever.Retriever
ffclient.KubernetesRetriever    ->      k8sretriever.Retriever
fflcient.S3Retriever            ->      s3retriever.Retriever

Exporters

ffexporter.File                 ->      fileexporter.Exporter
ffexporter.GoogleCloudStorage   ->      gcstorageexporter.Exporter
ffexporter.Log                  ->      logsexporter.Exporter
ffexporter.S3                   ->      s3exporter.Exporter
ffexporter.Webhook              ->      webhookexporter.Exporter

Notifiers

Since in this PR we change the way to work with notifier, you have more impact when configuring them.

Before this PR to configure a notifier you had something like that.

_, err := ffclient.New(ffclient.Config{
    // ...
    Notifiers: []ffclient.NotifierConfig{
        &ffclient.WebhookConfig{
            // ...
        },
    },
})

With this PR we had remove the ffclient.NotifierConfig struct to use directly the notifier them self.
It means that now ffclient.Config.Notifiers has the type []notifier.Notifier.
So it will look like:

_, err := ffclient.New(ffclient.Config{
    // ...
    Notifiers: []notifier.Notifier{
        &webhooknotifier.Notifier{
            // ...
        },
    },
})

To follow the same pattern has the retrievers and exporters we also have changed the struct you were using.

notifier.LogNotifier        ->      logsnotifier.Notifier
ffclient.SlackNotifier      ->      slacknotifier.Notifier
ffclient.WebhookConfig      ->      webhooknotifier.Notifier

Changes include

• Breaking changes (change that is not backward-compatible and/or changes current functionality)

Closes issue(s)

Resolve #256

Checklist

• I have tested this code
• I have added unit test to cover this code
• I have updated the documentation (README.md and /docs)
• I have followed the contributing guide

[coveralls]

Coverage increased (+0.4%) to 94.381% when pulling 691f2e1 on feat/move-retriever into e876781 on main.

[urso]

Thank you, the PR description is very detailed.

I only skimmed over the changes, but LGTM. Only nit is that the placing of the testdata feels a little non-idiomatic. As the exporters/retrievers/notifiers are more isolated now I would normally expect the testdata right next to each exporter. Like exporter/file/testdata and so on.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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