feat: add instrument package for Segment

[keiko713]

This PR adds the instrument package for Segment. You can enable this by having the following in the config file:

INSTRUMENT_ENABLED=true
INSTRUMENT_KEY=segment_api_key

Then, you can use this like the following:

instrument.Track("user_id", "my-event", properties)

If enabled is false (default false), you can still use this, but instead of the events sent out to Segment, it'll be logged to the logger.

[pandemicsyn]

I think it might be worth including some docs pointing netlify folks to https://github.com/netlify/segment-events to make sure internal users follow the processes and conventions mentioned there?

I like the visibility of having this package in netlify-commons, because this is probably the first place folks would look for it, but I wonder if this shouldn't be a package in the internal segment events repo?

[keiko713]

I think it might be worth including some docs pointing netlify folks to https://github.com/netlify/segment-events to make sure internal users follow the processes and conventions mentioned there?

In general, I like the idea of pointing to the doc. I think we can also improve our README to explain how to use each package too, and pointing to that repo is something we can do in there. How does that sound? I'm honestly little hesitate to add it to the codebase as a comment, so feels better if it was in README.

I like the visibility of having this package in netlify-commons, because this is probably the first place folks would look for it, but I wonder if this shouldn't be a package in the internal segment events repo?

Sooooo I'd disagree with having this package in segment-events repo. netlify-commons repo is providing the basic common features of our services and the instrumentation can be count as a basic feature, was my reasoning having this here. For example, we could implements more instrumentation client potentially in the future and swap out as the project needs.
The netlify/segment-events is also not really fitting to have the code/library in it, I feel like. It is really more of the documentation.
I see this instrument package a very similar to the featureflag package. We are providing the basic feature in the netlify-commons library, then we have documented our own rule for how to use it elsewhere.

[keiko713]

uhmm re: doc, actually maybe I should be adding more in the README but more in the code (as you can see it in https://pkg.go.dev/github.com/netlify/netlify-commons@v0.51.2/metriks).
I'll actually add more doc in the code and I'll see how it turns out

[keiko713]

doc output:

[rybit]

if you don't export these methods then you effectively have an interface you can't implement in a different client.

[keiko713]

🤦 yes