Add example of batch reading from Kafka with context propagation

[marijarin]

Closes #224

There is a difference between Kotlin and Java modules i.e. in Kotlin app trace ids are equal for single record and batch record listening though in Java apps they are different.
Also I didn't complete the work on increasing test coverage. Lines with forming error spans in KafkaReadingService are not covered. So I wrote a test for a non-reactive Java app, which solves partially this problem (it is KafkaTracingTest), but I am not sure of this one.

[marijarin]

I found a checkstyle problem in build, but need some time to solve it as after merging master branch got a Gradle error
Required by: project :buildSrc > Could not resolve io.freefair.gradle:lombok-plugin:8.14.2. > Could not get resource 'https://plugins.gradle.org/m2/io/freefair/gradle/lombok-plugin/8.14.2/lombok-plugin-8.14.2.pom'. > Could not GET 'https://plugins.gradle.org/m2/io/freefair/gradle/lombok-plugin/8.14.2/lombok-plugin-8.14.2.pom'. > Got SSL handshake exception during request. It might be caused by SSL misconfiguration > PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

I tried to reset HEAD then rearrange imports and after that remerge master to fix checkstyle errors, but need some time to fix this error. May be it won't appear in my Linux laptop

UPD the problem was with Gradle JVM

[codecov]

Codecov Report

❌ Patch coverage is 99.03846% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.54%. Comparing base (fc50dce) to head (6e3d9dc).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...g/boot3/kotlin/test/service/KafkaReadingService.kt	96.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #311      +/-   ##
============================================
+ Coverage     94.24%   96.54%   +2.29%     
- Complexity      110      135      +25     
============================================
  Files            39       42       +3     
  Lines           313      376      +63     
  Branches         10        8       -2     
============================================
+ Hits            295      363      +68     
+ Misses           10        7       -3     
+ Partials          8        6       -2     

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