[improve][build] Add lombok plugin to solve Javadoc issue.

[Technoboy-]

Motivation

When releasing branch-2.11, there is a issue when generating Javadoc :

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.0.1:javadoc (default-cli) on project pulsar-functions-api: An error has occurred in Javadoc report generation: 
[ERROR] Exit code: 1 - Loading source files for package org.apache.pulsar.functions.api...
[ERROR] Loading source files for package org.apache.pulsar.functions.api.utils...
[ERROR] Loading source files for package org.apache.pulsar.functions.api.state...
[ERROR] Constructing Javadoc information...
[ERROR] /Users/tboy/tboy/workspace_3/pulsar/pulsar-functions/api-java/src/main/java/org/apache/pulsar/functions/api/Context.java:173: error: cannot find symbol
[ERROR]     <X> FunctionRecord.FunctionRecordBuilder<X> newOutputRecordBuilder(Schema<X> schema);
[ERROR]                       ^
[ERROR]   symbol:   class FunctionRecordBuilder
[ERROR]   location: class FunctionRecord
[ERROR] /Users/tboy/tboy/workspace_3/pulsar/pulsar-functions/api-java/src/main/java/org/apache/pulsar/functions/api/utils/FunctionRecord.java:52: error: cannot find symbol
[ERROR]     public static <T> FunctionRecord.FunctionRecordBuilder<T> from(Context context, Schema<T> schema) {
[ERROR]                                     ^
[ERROR]   symbol:   class FunctionRecordBuilder
[ERROR]   location: class FunctionRecord
[ERROR] 2 errors
[ERROR] 
[ERROR] Command line was: /Library/Java/JavaVirtualMachines/jdk-17.0.3.1.jdk/Contents/Home/bin/javadoc @options @packages
[ERROR] 
[ERROR] Refer to the generated Javadoc files in '/Users/tboy/tboy/workspace_3/pulsar/pulsar-functions/api-java/target/site/apidocs' dir.

We can use mvn javadoc:javadoc to reproduce in the master branch.

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

[codecov-commenter]

Codecov Report

Merging #18520 (ae7edfe) into master (aeb4503) will increase coverage by 3.67%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master   #18520      +/-   ##
============================================
+ Coverage     31.39%   35.06%   +3.67%     
- Complexity     6651     6654       +3     
============================================
  Files           697      617      -80     
  Lines         68015    58514    -9501     
  Branches       7285     6099    -1186     
============================================
- Hits          21353    20519     -834     
+ Misses        43667    35268    -8399     
+ Partials       2995     2727     -268     

Flag	Coverage Δ
unittests	35.06% <ø> (+3.67%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...on/buffer/impl/InMemTransactionBufferProvider.java	0.00% <0.00%> (-50.00%)	⬇️
...java/org/apache/pulsar/proxy/stats/TopicStats.java	58.82% <0.00%> (-41.18%)	⬇️
...ker/loadbalance/impl/LeastLongTermMessageRate.java	64.44% <0.00%> (-6.67%)	⬇️
...sar/broker/loadbalance/impl/LoadManagerShared.java	35.96% <0.00%> (-2.20%)	⬇️
...roker/loadbalance/impl/ModularLoadManagerImpl.java	61.53% <0.00%> (-1.18%)	⬇️
...a/org/apache/pulsar/proxy/server/ProxyService.java	80.00% <0.00%> (-0.94%)	⬇️
...apache/pulsar/proxy/server/LookupProxyHandler.java	57.75% <0.00%> (-0.44%)	⬇️
...e/bookkeeper/mledger/impl/NullLedgerOffloader.java
...mledger/impl/cache/RangeEntryCacheManagerImpl.java
...va/org/apache/bookkeeper/mledger/util/SafeRun.java
... and 175 more

[lhotari]

@Technoboy- Did this PR solve the issue?
Just wondering about the docs in http://anthonywhitford.com/lombok.maven/lombok-maven-plugin/usage.html:

Place the java source code with lombok annotations in src/main/lombok (instead of src/main/java). During the build process, the src/main/lombok code will be delomboked and the generated java code ends up in target/generated-sources/delombok. The delomboked code is compiled and analysed together with the src/main/java code.

[tisonkun]

@Technoboy- I think this the root cause that the generated javadoc for 2.11.0 using pytools becomes empty.