Fix #13385 spring json nullable array (!13537) · Merge requests · OpenAPI Tools / openapi-generator

Created by: DeaneOC

Updated SpringCodeGen to handle nullable Arrays correctly. This fixes issue #13385 (closed).

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Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
Run the following to build the project and update samples:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
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@cachescrubber @welshm @MelleD @atextor @manedev79 @javisst @borsch @banlevente @Zomzog

I'd love some advice on what is the correct branch to merge into for this change.

Contributed on behalf of the @opencastsoftware open source team. 👋