[BUG] [kotlin-spring] wrong field name and type for multipart

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Code generator "kotlin-spring" generates incorrect field names and types for requestBody "multipart/form-data". All parts which are defines of type string and format binary gets name "file" and type "org.springframework.core.io.Resource".

The same code is generated correct with generator "spring". All parts gets correct name and type of "MultipartFile".

Here is the result of generated file:

 @RequestMapping(
            method = [RequestMethod.PUT],
            value = ["/test"],
            produces = ["application/json"],
            consumes = ["multipart/form-data"]
    )
    fun saveResource(acceptLanguage: kotlin.String, @Valid @RequestPart("file") myImages: kotlin.collections.List<org.springframework.core.io.Resource>, @RequestParam(value = "jsonObject", required = true) jsonObject: JsonObjectDto, @Valid @RequestPart("file") image1: org.springframework.core.io.Resource?, @Valid @RequestPart("file") image2: org.springframework.core.io.Resource?): ResponseEntity<JsonObjectDto> {
        return ResponseEntity(HttpStatus.NOT_IMPLEMENTED)
    }

openapi-generator version

"org.openapitools":"openapi-generator-maven-plugin":"6.5.0"

OpenAPI declaration file content

/test:
  put:
      operationId: saveResource
      parameters:
        - name: Accept-Language
          in: header
          schema:
            type: string
          required: true
      requestBody:
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                image1:
                  type: string
                  format: binary
                image2:
                  type: string
                  format: binary
                myImages:
                  type: array
                  maxItems: 10
                  items:
                    type: string
                    format: binary
                jsonObject:
                  $ref: '#/components/schemas/JsonObjectDto'
              required:
                - jsonObject
                - myImages
       responses:
         '200':
           content:
             application/json:
               schema:
                 $ref: '#/components/schemas/JsonObjectDto'
components:
  schemas:
    JsonObjectDto:
    type: object
    properties:
      id:
        type: string
      name:
        type: string        

Generation Details

generated using maven plugin

<plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>6.5.0</version>
                <executions>
                    <execution>
                        <id>gen-svc-models</id>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/myapp.yaml</inputSpec>
                            <generatorName>kotlin-spring</generatorName>
                            <configOptions>
                                <useTags>true</useTags>
                                <basePackage>com.mypackage</basePackage>
                                <apiPackage>com.mypackage.api</apiPackage>
                                <modelPackage>com.mypackage.model</modelPackage>
                                <configPackage>com.mypackage.config</configPackage>
                                <documentationProvider>none</documentationProvider>
                                <exceptionHandler>false</exceptionHandler>
                                <interfaceOnly>true</interfaceOnly>
                                <enumPropertyNaming>UPPERCASE</enumPropertyNaming>
                                <useSpringBoot3>true</useSpringBoot3>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Steps to reproduce

Attempting to generate kotling spring interface using given maven plugin and contract generates incorrect types and names of multipart.

No repository file or test is named. First reproduce the issue with the supplied OpenAPI declaration using the kotlin-spring generator, then compare its multipart output with the spring generator. Done means each binary part retains its declared name and uses the expected multipart type.