Split project into modules

[iRevive]

Follow up to #29 (comment).

The new structure is the following:

core:
  core-common
  core-metrics (depends on core-common)
  
testkit:
  testkit-common (depends on core-common)
  testkit-metrics (depends on testkit-common and core-metrics)
  
java:
  java-common (depends on core-common and testkit-common)
  java-metrics (depends on java-common, core-mertics, and testkit-metrics)

That way adding new modules (i.e. tracing, logging) should be easier.

[armanbilge]

Suggested change

	lazy val `java-common` = crossProject(JVMPlatform)
	.crossType(CrossType.Pure)
	lazy val `java-common` = project

[iRevive]

Looks better now, thanks

[armanbilge]

Suggested change

	.dependsOn(`core-common`, `testkit-common`)
	.dependsOn(`core-common`.jvm, `testkit-common`.jvm)

[armanbilge]

Should the module name be meta maybe? Typically the module name and package name are somehow matching.

[armanbilge]

Also, is this file misplaced? Or maybe I'm very confused by the source reorganizaiton 🤔

[armanbilge]

Ah, sorry, ignore me 😂

[armanbilge]

Do we need full IO here, should it be ce-kernel or ce-std? Does it matter (it won't if we add fs2 deps). Do we care?

[iRevive]

Good point. Actually, cats-effect-kernel is enough.

I was thinking about fs2 dependency in tracing module recently. Unless we want to introduce some deep tracing for stream scopes (I'm not even sure how plausible it is) the scodec is more than enough.

[rossabaker]

I played with extending stream tracing to Natchez, and concluded that having a way to trace Resource was good enough for streams. All a stream dependency brings is a convenience method around Stream.resource(whateverCreatesTheSpan).

[iRevive]

Yeah, once a streaming scope is described as a Resource, the propagation works well with streams.

otel4s/java/src/test/scala/org/typelevel/otel4s/java/trace/TracerSuite.scala

Lines 467 to 483 in d70a57d

	def flow(tracer: Tracer[IO]): Stream[IO, Unit] =
	for {
	span <- Stream.resource(tracer.span("span"))
	_ <- Stream.eval(
	tracer.currentSpanContext.assertEquals(Some(span.context))
	)
	span2 <- Stream.resource(tracer.span("span-2"))
	_ <- Stream.eval(
	tracer.currentSpanContext.assertEquals(Some(span2.context))
	)
	span3 <- Stream.resource(
	tracer.spanBuilder("span-3").withParent(span.context).createAuto
	)
	_ <- Stream.eval(
	tracer.currentSpanContext.assertEquals(Some(span3.context))
	)
	} yield ()

[iRevive]

@zmccoy sorry for pinging you personally, but would you be interested in reviewing this PR as well?

There was a discussion regarding the modularity of the project #29 (comment).

And I would prefer to resolve this one before #36.

[zmccoy]

This looks great!

[iRevive]

@rossabaker could you have a moment to review this PR, please?

[rossabaker]

This looks great to me. I'm sorry I fell into a hole for several weeks.

[rossabaker]

I think you can use a pipe operator if you want it to say meters but link to Meter:

[[org.typelevel.otel4s.metrics.Meter|meters]]

That should not slow this down.

[iRevive]

doc command was failing. I do not remember the exact reason, but I will bring back the link if it's possible.

[armanbilge]

@iRevive you should just use a space there, not a |.