[java] Intro openApiNullable property to enable/disable OpenAPI Jackson Nullable library (#6154)

* Add option to prevent usage of jackson-nullable (#2901)

Add a option for all java client and server to prevent
usage of third party library (jackson-databind-nullable)
which may be forbidden in some company

Add samples for Vertx, Spring MVC, Spring Cloud, Feign and Play

Upgrade dependencies for org.openapitools:jackson-databind-nullable

* Samples - Remove dependency org.openapitools:jackson-databind-nullable (#2901)

* Fix generation of gradle file for vertx (#2901)

* Regenerate samples (#2901)

* Fix documentation and up to date (#2901)

* Fix forgotten regeneration of vertx after dependency integration (#2901)

* Regenerate template after rebase (#2901)

* Use yaml config files introduce in #6509 to manage samples (#2901)

* Regenerate template using the config (#2901)

* Fix bad version during testing generated samples (#2901)

* Regenerate template after fix bad version (#2901)

* Fix merge, allow for set importing on codegen model

Co-authored-by: Jim Schubert <james.schubert@gmail.com>

docs/generators/java.md

@@ -36,6 +36,7 @@ sidebar_label: java
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |microprofileFramework|Framework for microprofile. Possible values "kumuluzee"| |null|
 |modelPackage|package for generated models| |org.openapitools.client.model|
+|openApiNullable|Enable OpenAPI Jackson Nullable library| |true|
 |parcelableModel|Whether to generate models for Android that implement Parcelable with the okhttp-gson library.| |false|
 |parentArtifactId|parent artifactId in generated pom N.B. parentGroupId, parentArtifactId and parentVersion must all be specified for any of them to take effect| |null|
 |parentGroupId|parent groupId in generated pom N.B. parentGroupId, parentArtifactId and parentVersion must all be specified for any of them to take effect| |null|