[BUG][Java][Spring] multiple files upload

Created by: purple-dragon

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
What's the version of OpenAPI Generator used?
Have you search for related issues/PRs?
What's the actual output vs expected output?
[Optional] Bounty to sponsor the fix (example)

Description

use open api spec 3 to define api to upload multiple files, but openapi generator generate incorrect, following openapi spec

https://swagger.io/specification/#mediaTypeObject section: "To upload multiple files, a multipart media type MUST be used:"

default ResponseEntity<Document> createDocument(@ApiParam(value = "file detail") @Valid @RequestPart("file") MultipartFile file,@ApiParam(value = "") @RequestParam(value="metadata", required=false)  Object metadata)

should be array: MultipartFile[] file

default ResponseEntity<Document> createDocument(@ApiParam(value = "file detail") @Valid @RequestPart("file") MultipartFile[] file,@ApiParam(value = "") @RequestParam(value="metadata", required=false)  Object metadata)

openapi-generator version

    <dependency>
        <groupId>org.openapitools</groupId>
        <artifactId>openapi-generator</artifactId>
        <version>4.2.2</version>
    </dependency>

OpenAPI declaration file content or url

openapi: "3.0.2"
info:
  version: "1.0.0"
  title: "File Management API"
  description: >-
    File Management

paths:
  /api/v1/documents:
    post:
      tags:
        - Manage Files
      summary: "Upload new file"
      operationId: "createDocument"
      requestBody:
        content:
          multipart/form-data:
            schema:
              properties:
                file:
                  type: array
                  items:
                    type: string
                    format: binary
                metadata:
                  type: object
      responses:
        201:
          description: "Document created, return generated document information"
        404:
          description: "Not Found"
        409:
          description: "Conflict"
        500:
          description: "Internal Server Error"

Command line used for generation

Steps to reproduce

Related issues/PRs

looks like there are similar issues, not sure if it fixed or not.

https://github.com/OpenAPITools/openapi-generator/issues/2210 https://github.com/ga4gh/workflow-execution-service-schemas/issues/43