[BUG][Java][Spring] implicitHeaders replace the - in header name by a camelCased name

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

Using the maven plugin configuration with implicitHeaders and with this API specification :

openapi: 3.0.2
info:
  title: Whatever
  version: 1.0.0
paths:
  /Whatever:
    summary: Get Whatever
    parameters:
      - name: 'X-Whatever-Code'
        in: header
        required: true
        description: Whatever
        allowEmptyValue: false
        schema:
          type: string
    get:
      responses:
        '200':
          description: Whatever
          content:
            application/json:
              schema:
                type: string

The name of the implicit param is defined to xWhateverCode instead of X-Whatever-Code

  @ApiImplicitParams({
    @ApiImplicitParam(name = "xWhateverCode", value = "Whatever", required=true, dataType = "String", paramType = "header"),
    })

openapi-generator version

4.3.1

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  title: Whatever
  version: 1.0.0
paths:
  /Whatever:
    summary: Get Whatever
    parameters:
      - name: 'X-Whatever-Code'
        in: header
        required: true
        description: Whatever
        allowEmptyValue: false
        schema:
          type: string
    get:
      responses:
        '200':
          description: Whatever
          content:
            application/json:
              schema:
                type: string

Generation Details

<plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>4.3.1</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <output>${openapi.generation.directory}</output>
                            <inputSpec>src/main/resources/openapi.yaml</inputSpec>
                            <generatorName>spring</generatorName>
                            <apiPackage>com.whatever.api.controller</apiPackage>
                            <modelPackage>com.whatever.api.model</modelPackage>
                            <generateSupportingFiles>false</generateSupportingFiles>
                            <configOptions>
                                <sourceFolder>.</sourceFolder>
                                <groupId>whatever</groupId>
                                <invokerPackage>com.whatever.api</invokerPackage>
                                <dateLibrary>java8</dateLibrary>
                                <artifactId>whatever-api</artifactId>
                                <artifactVersion>1.0.0</artifactVersion>
                                <configPackage>com.whatever.configuration</configPackage>
                                <basePackage>com.whatever</basePackage>
                                <reactive>true</reactive>
                                <interfaceOnly>true</interfaceOnly>
                                <skipDefaultInterface>true</skipDefaultInterface>
                                <implicitHeaders>true</implicitHeaders>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

Steps to reproduce

Simply generate the source code with the configurations above

Related issues/PRs

Seems to be a similar problem with Kotlin generation : https://github.com/OpenAPITools/openapi-generator/issues/7322

Suggest a fix

Start with the Spring generator entry point used by the Maven plugin and trace how the implicitHeaders option converts the OpenAPI header name X-Whatever-Code. Reproduce the issue with the provided OpenAPI 3.0.2 specification and Spring configuration, then verify that generated @ApiImplicitParam metadata preserves the expected header name and add or update the relevant generator test if one is found.