Migrate to OTEL libraries

[alejandrodnm]

Since the Jaeger SDK is deprecated use instead the OTEL SDK with the
Jaeger exporter.

[yurishkuro]

This PR unnecessarily large. Please split into independent pieces, eg

1. Introduce go.mod
2. Add OTEL SDK

and I don't see a need to move the files into pkg, why is that needed?

[alejandrodnm]

@yurishkuro yeah you're right.

I planned to do a first PR for the god modules, but got some errors on the Jaeger packages and then the PTSD of working with go vendor kicked in D: so I thought, if I use the latest packages from OTEL it must surely work with go modules.

I'll split it.

The moving into pkg and cmd is because I thought that was the standard way of managing go projects, I'll keep it as is.

[yurishkuro]

The moving into pkg and cmd is because I thought that was the standard way of managing go projects, I'll keep it as is.

cmd/pkg convention makes more sense for monorepo-style projects like Jaeger backend that produces a lot of different binaries. In this repo it provides no benefits.

[yurishkuro]

Thanks for go.mod change btw, I even forgot that this repo is still on dep.

[yurishkuro]

Awesome!

Selfish ask - maybe you're interested in jaegertracing/jaeger#3380 ? :-)

[yurishkuro]

Another option is to start using OTLP as exporter instead of Jaeger format, because Jaeger backend can already accept it. Or make it an option to switch between jaeger and otlp. But not in this PR.