Tracing support

[vietj]

Vert.x 4 supports tracing.

Fixes #653

[vietj]

Pushed a new approach wiring the tracing in the client layer instead of the connection layer as the tracing cares about the client context before all.

[BillyYccc]

We're also missing db.url tag, it could be added if we support exporting sqlConnectOptions to a connection url.

[vietj]

db.url tag is not defined by opentracing and it is actually a Java-ish thing inherited from JDBC so I'm not sure we need that for the moment, e.g you don't have such tag if you have a JavaScript microservice

[BillyYccc]

db.url is required in OpenTelemetry spec https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/semantic_conventions/database.md

It's not hard to support this after #644,
we could get SqlConnectOptions transformed into a short url like [dbkind]://[username]@[host]:[port]/[databasename]

[vietj]

please don't name that kind :-)

[vietj]

kind is typically the name you use when you can't find a good name :-)

[BillyYccc]

I couldn't find an appropriate name for that either so I use it to show the usage 😅

[BillyYccc]

Overall it looks very good as the first version after we settle the minor changes.

[vietj]

@BillyYccc as for naming and tags, I believe we need to have in master a definition of the tags we are going to use commonly in this project so each tracing integration can do a mapping of such tag to its own tagging system.

There are chances we will use the opentracing and/or opentelemetry list and then figure out. And then we will revisit this project for naming if required.

[vietj]

I think the right name is dbms or rdbms