* [kotlin-spring] Generate @Valid annotation on all RequestParts/Params for Multipart requests when useBeanValidation=true
* [kotlin-spring] Fix failing test
The test was failing because of the newly added @Valid and an assert which is not correct anymore.
* replace removed forkMode
* remove junit runner where it's not needed
* update samples without skipping test files, but skip files named "FILES"
* revert overwriting custom tests, add custom java tests to list
* add one sample to CircleCI, fix various Java tests
* [kotlin-spring] Fix no List being used for an array of files using multipart/form-data
* [kotlin-spring] Use Spring's MultipartFile class for incoming Files instead of Spring's Resource class.
* [kotlin-spring] Add test to ensure that return type for files is `org.springframework.core.io.Resource`
* [kotlin-spring] Ensure Array is used for lists of files in generated Api class
* Update samples
* [kotlin-spring] Move conditional usage of MultipartFile to optionalDataType.mustache. Update samples
* update samples
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Co-authored-by: William Cheng <wing328hk@gmail.com>
