[Tracing] Support to Jaeger and OpenTracing

[SimoneGiusso]

Hi,

I'm using lettuce as Redis (reactive) client API by means of ReactiveRedisTemplate.

For tracing I'm using:

<groupId>io.jaegertracing</groupId>
<artifactId>jaeger-client</artifactId>

<groupId>io.opentracing.contrib</groupId>
<artifactId>opentracing-spring-cloud-starter</artifactId>

Looking at the documentation is clear that this project supports only Brave.

However Lettuce ships with a Tracing SPI in io.lettuce.core.tracing that allows custom tracer implementations. Is there an implementation of this interface ready to use?