[BUG][JAVA][webclient] UnsupportedMediaTypeException if multiple consumes media type and unknown type in first position

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

Template : Java/webclient

We generated client side code in Java/webclient mode for an api which define multiples media types in 'consumes' part. The swagger file is like the following (I omitted the unuseful parts) :

{
  "swagger": "2.0",
  "paths": {
    "/mypath": {
      "post": {
        "operationId": "post",
        "consumes": [          
          "application/json-patch+json",
          "application/json",
          "text/json",
          "application/*+json"
        ],
        "produces": [
          "application/json"
        ]
                      }
                }
      }
}

The important thing is the order of the consumes list. The first value in the example is "application/json-patch+json". In this case, the execution of the generated webclient code throws the following error :

org.springframework.web.reactive.function.UnsupportedMediaTypeException: Content type 'application/json-patch+json' not supported for bodyType=MyObject
    at org.springframework.web.reactive.function.BodyInserters.unsupportedError(BodyInserters.java:391)
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException:

If the first value is "application/json", everything works fine.

openapi-generator version

5.0.0

OpenAPI declaration file content or url

Generation Details

below our maven configuration to generate the java webclient code :

<plugin>
				<groupId>org.openapitools</groupId>
				<artifactId>openapi-generator-maven-plugin</artifactId>
                                <version>5.0.0</version>
				<executions>
					<execution>
						<id>swagger</id>
						<goals>
							<goal>generate</goal>
						</goals>
						<configuration>
							<invokerPackage>${utilPackage}</invokerPackage>
							<generateModelTests>false</generateModelTests>
							<generateApiTests>false</generateApiTests>
							<generateSupportingFiles>true</generateSupportingFiles>
							<modelPackage>${modelPackage}</modelPackage>
							<apiPackage>${clientPackage}</apiPackage>
							<generatorName>java</generatorName>
							<inputSpec>${project.basedir}/src/main/swagger/swagger.json</inputSpec>
							<generateModelDocumentation>false</generateModelDocumentation>
							<configOptions>
								<library>webclient</library>
								<serializableModel>true</serializableModel>
								<interfaceOnly>true</interfaceOnly>
								<java8>true</java8>
								<dateLibrary>java8</dateLibrary>
								<performBeanValidation>true</performBeanValidation>
								<useBeanValidation>true</useBeanValidation>
								<serializationLibrary>jackson</serializationLibrary>
								<serializableModel>true</serializableModel>
							</configOptions>
						</configuration>
					</execution>
				</executions>
			</plugin>

Steps to reproduce

Related issues/PRs

Suggest a fix

In client-side, if a content-type is unknown, doesn't throw an exception and try the next one.

Start with the generated Java/webclient client produced by the Maven configuration and reproduce the issue using the shown consumes order. Trace how the client selects a request content type when the first type is unsupported; done means an unknown first type is skipped so a supported type is tried without UnsupportedMediaTypeException.