Encoding object only sets first encoding annotation

[jeremyfiel]

Describe the bug

related #532
cc @patrykpacewicz

Seems the PR that introduced this support only captures the first @Encoding definition. It's possible to have more than one.

package org.example.springbased.web;

import io.swagger.v3.oas.annotations.Parameter;
import io.swagger.v3.oas.annotations.media.Content;
import io.swagger.v3.oas.annotations.media.Encoding;
import io.swagger.v3.oas.annotations.parameters.RequestBody;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

@RestController
@RequestMapping("/test")
public class TestController {

@PostMapping(value ="/first", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public ResponseEntity<String> uploadMultipartWithBody(
        @RequestBody(content = @Content(encoding = @Encoding(name = "file", contentType = MediaType.APPLICATION_OCTET_STREAM_VALUE)))
        @Parameter(required = true)
        @RequestPart("file") MultipartFile file,
        @RequestBody(content = @Content(encoding = @Encoding(name = "dto", contentType = MediaType.APPLICATION_JSON_VALUE)))
        @Parameter(description = "An extra JSON payload sent with file")
        @RequestPart("dto")
        DTO dto){
        return ResponseEntity.ok("Request Accepted: " + dto.toString());
    }
}}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springdoc:springdoc-openapi-starter-webmvc-ui:2.8.6'
    implementation 'org.springframework.boot:spring-boot-devtools'
}

To Reproduce
Steps to reproduce the behavior:

Expected behavior

The output should include both encoding definitions.

requestBody:
  content:
    'multipart/form-data':
      schema:
        type: object
        required:
          - dto
          - file
        properties:
          dto:
            type: string
          file:
            type: string
            format: binary
      encoding:
        file:
          contentType: application/octet-stream
        dto:
          contentType: application/json
        

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Additional context
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