[BUG] [jaxrs-spec] FormParam used instead of FormDataParam for "multipart/form-data"

Bug Report Checklist

Description

jaxrs-spec generator adds javax.ws.rs.FormParam annotation to parameters when content type is set to multipart/form-data

It causes the following error with Jersey (jaxrs reference implementation) for primitive types:

java.lang.IllegalStateException: The @FormParam is utilized when the content type of the request entity is not application/x-www-form-urlencoded
        at org.glassfish.jersey.server.internal.inject.FormParamValueParamProvider$FormParamValueProvider.ensureValidRequest(FormParamValueParamProvider.java:107)

When javax.ws.rs.FormParam is applied to a Java bean, Jersey throws a different error:

org.glassfish.jersey.server.model.ModelValidationException: Validation of the application resource model has failed during application initialization.
[[FATAL] No injection source found for a parameter of type public abstract javax.ws.rs.core.Response com.foo.FooApi.addFoo(com.foo.FooDto) at index 0.; source='ResourceMethod{httpMethod=POST, consumedTypes=[multipart/form-data], producedTypes=[application/json], suspended=false, suspendTimeout=0, suspendTimeoutUnit=MILLISECONDS, invocable=Invocable{handler=ClassBasedMethodHandler{handlerClass=interface com.foo.FooApi handlerConstructors=[]}, definitionMethod=public abstract javax.ws.rs.core.Response com.foo.FooApi.addFoo(com.foo.FooDto), parameters=[Parameter [type=class com.foo.FooDto, source=metadata, defaultValue=null]], responseType=class javax.ws.rs.core.Response}, nameBindings=[]}']
        at org.glassfish.jersey.server.ApplicationHandler.initialize(ApplicationHandler.java:371) ~[jersey-server-2.29.1.jar:na]

openapi-generator version

openapi-generator-maven-plugin 4.3.0 with jaxrs-spec generator

OpenAPI declaration file content or url

For simple parameter:

   requestBody:
     content:
         multipart/form-data:
            schema:
              properties:
                foo:
                  type: integer
                  format: int32

For bean parameter:

   requestBody:
     content:
         multipart/form-data:
            schema:
              type: object
              properties:
                metadata:
                   $ref: '#/components/schemas/FooDto'

Command line used for generation

openapi-generator-maven-plugin with jaxrs-spec generator

Steps to reproduce

1. Generate API with openapi-generator-maven-plugin and jaxrs-spec generator
2. Implement the API
3. Add org.springframework.boot:spring-boot-starter-jersey and org.glassfish.jersey.media:jersey-media-multipart to your project
4. In JerseyConfig add register(MultiPartFeature.class);
5. Try invoking generated endpoints. It will return the error described above
6. (optional) Manually change the annotation in generated classes to FormDataParam and check that it works.

Related issues/PRs

Suggest a fix

I checked that when javax.ws.rs.FormParam is replaced with org.glassfish.jersey.media.multipart.FormDataParam, everything works fine.

However, org.glassfish.jersey.media.multipart.FormDataParam is Jersey specific.
Maybe there should be a configuration option to choose which annotation should be used for multi part parameters.

More about Multipart in Jersey:
https://eclipse-ee4j.github.io/jersey.github.io/documentation/latest/media.html#multipart

Start with the jaxrs-spec generator's handling of multipart/form-data request parameters and reproduce the issue using the provided OpenAPI YAML and Jersey setup. Compare generated FormParam usage with the manually verified FormDataParam behavior; done should mean multipart endpoints work for both primitive and bean parameters without breaking non-Jersey behavior.