Java SDK: Static analysis

[booniepepper]

Consider adding PMD and/or SpotBugs checks to the generated SDK

[booniepepper]

Note just adding id 'pmd' to the build.gradle with no other configuration leads to quite a few violations.

> Task :compileJava
Note: /module/src/main/java/dev/openfga/api/invoker/JSON.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

> Task :processResources NO-SOURCE
> Task :classes
> Task :jar
> Task :javadoc
> Task :javadocJar
> Task :sourcesJar
> Task :assemble
> Task :compileIntegrationJava
> Task :processIntegrationResources NO-SOURCE
> Task :integrationClasses
> Task :compileTestJava
> Task :processTestResources NO-SOURCE
> Task :testClasses
> Task :pmdIntegration FAILED
> Task :test
> Task :pmdTest FAILED
> Task :pmdMain FAILED

FAILURE: Build completed with 3 failures.

1: Task failed with an exception.
-----------
* What went wrong:
Execution failed for task ':pmdIntegration'.
> A failure occurred while executing org.gradle.api.plugins.quality.internal.PmdAction
   > 7 PMD rule violations were found. See the report at: file:///module/build/reports/pmd/integration.html

* Try:
> Run with --scan to get full insights.
==============================================================================

2: Task failed with an exception.
-----------
* What went wrong:
Execution failed for task ':pmdTest'.
> A failure occurred while executing org.gradle.api.plugins.quality.internal.PmdAction
   > 13 PMD rule violations were found. See the report at: file:///module/build/reports/pmd/test.html

* Try:
> Run with --scan to get full insights.
==============================================================================

3: Task failed with an exception.
-----------
* What went wrong:
Execution failed for task ':pmdMain'.
> A failure occurred while executing org.gradle.api.plugins.quality.internal.PmdAction
   > 641 PMD rule violations were found. See the report at: file:///module/build/reports/pmd/main.html

* Try:
> Run with --scan to get full insights.
==============================================================================

16 actionable tasks: 16 executed
BUILD FAILED in 38s
make[1]: *** [run-in-docker] Error 1
make: *** [build-client-java] Error 2