Fix issue 11731

[networkinss]

Fixes #11731.
Added a test in:
src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
doGenerateMediatypes()
including the test openapi yaml in:
src/test/resources/3_0/spring/issue_11731.yaml
Fix is in the spring mustache file:
src/main/resources/JavaSpring/methodBody.mustache
line 9 & 11.

PR checklist

./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh

Done and commited.

@cachescrubber (2022/02)
@welshm (2022/02)
@MelleD (2022/02)
@atextor (2022/02)
@manedev79 (2022/02)
@javisst (2022/02)
@borsch (2022/02)
@banlevente (2022/02)

[networkinss]

My fix is not correct yet.
If works if there is just one mediatype.
But it fails for multiple media types, as could be seen for the failed sample generations.
My mustace experience is probably unsufficient to make it correct now.

[tamershahin]

this is quite crucial for us.. is there any plan to resume the work on it?

[networkinss]

I can give it another try in the next days.

[tamershahin]

I can give it another try in the next days.

pls have a look here it looks like @borsch may help you there :)