Vert.x WebClient instrumentation

[AlexanderWert]

Extended Vert.x instrumentation with instrumentation for Vert.x Web Client.

Notes:

• Didn't use the tracer approach for version 4 as this does not allow to handle instrumentation of redirects properly.

• Instrumentation approach is similar for all versions

• had to fix Vert.x core instrumentation for setTimer context propagation: avoid instrumentation of directly recursive setTimer invocations (as this is a common pattern for endless checks)

• Added to CHANGELOG

• Added to supported technologies page

[ghost]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Build Cause: Pull request #1824 updated

• Start Time: 2021-06-09T13:36:14.935+0000

• Duration: 54 min 14 sec

• Commit: 8afd326

Test stats 🧪

Test	Results
Failed	0
Passed	2245
Skipped	18
Total	2263

Trends 🧪

💚 Flaky test report

Tests succeeded.

Expand to view the summary

Test stats 🧪

Test	Results
Failed	0
Passed	2245
Skipped	18
Total	2263

[eyalkoren]

I will take over from here, thanks @AlexanderWert!

[eyalkoren]

@AlexanderWert it is ready as far as I am concerned.
Please go over the changes I've made to make sure they make sense.

I fixed the fail() API instrumentation (decrementing references for the parent span so that it can be reported) and added a test. In addition, I made sure that we at least capture an error for this scenario. Currently, a span is reported with all the details for failed requests only in Vert.x 3. We can add this capability to Vert.x 4 as well, but it will be messy - we will need to rely on internal fields for that (see details) so I decided an error will do for now 🙂 .

[AlexanderWert]

@eyalkoren: LGTM, I'm fine with merging!