Add support for jaeger propagation formats

[vladislav-kiva]

Is your feature request related to a problem? Please describe.
Problem: In our company we have an existing ecosystem of around 50 microservices per domain. Practically all instrumented with existing jaeger libraries and they are using jaeger standards like uber-trace-id HTTP header and so on.

Describe the solution you'd like
I think we should implement smth like JaegerHttpTraceFormat.ts near B3Format.ts and HttpTraceContext.ts. That would allow us to work with jaeger format's and we can switch between formats via configuration

[OlivierAlbertini]

If I understand correctly, you can do it like:

1. Implementing HttpTextFormat interface.
2. passing the concrete class to the NodeTracer config like :

new NodeTracer({
httpTextFormat: new MyCustomHttpTextFormat()
})

JaegerHttpTraceFormat is already very close to HttpTextFormat interface

[dyladan]

HttpTextFormat interface is just an interface that your formatter must conform to. There is a text format and a binary format interface. You should implement the text format interface. I think @OlivierAlbertini was referring to the HttpTraceContext which is very close to the Jaeger format.

[dyladan]

I removed the target label because this could be used for both web and node.

[mayurkale22]

We can re-use code from OpenCensus: https://github.com/census-instrumentation/opencensus-node/tree/master/packages/opencensus-propagation-jaeger

[dyladan]

@vladislav-kiva are you implementing this?

[vmarchaud]

@dyladan He wrote on the node gitter that he started to work on that, hence i assigned it to him

[vladislav-kiva]

@dyladan yeap for now i already wrote it and now i'm writing tests|

[vladislav-kiva]

@mayurkale22 thanks i will take a look on it, for now i was using https://github.com/jaegertracing/jaeger-client-node