[BUG][dart][dart-dio] "--api-name-suffix" and "--model-name-suffix" options have no effect on generation

Created by: valebedu

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
What's the version of OpenAPI Generator used?
Have you search for related issues/PRs?
What's the actual output vs expected output?
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Description

openapi-generator version

os: macOS os version: 10.15.2 openapi-generator version: 4.2.3 node version: 10.15.2 npm version: 6.13.4

OpenAPI declaration file content or url

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/test/resources/3_0/petstore.yaml

Command line used for generation

npm install
npm run client:generate

with the following package.json

{
  "name": "dart-dio-gen",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "client:generate": "rm -rf client/ && openapi-generator generate --generator-name dart-dio --api-name-suffix Api --model-name-suffix ApiModel --input-spec petstore.yaml --output client/"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@openapitools/openapi-generator-cli": "^1.0.10-4.2.3"
  }
}

Steps to reproduce

After generation, just have a look at client/model/user.dart for example

Obtained generate file:

        import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

part 'user.g.dart';

abstract class User implements Built<User, UserBuilder> {

    
        @nullable
    @BuiltValueField(wireName: r'id')
    int get id;
    
        @nullable
    @BuiltValueField(wireName: r'username')
    String get username;
    
        @nullable
    @BuiltValueField(wireName: r'firstName')
    String get firstName;
    
        @nullable
    @BuiltValueField(wireName: r'lastName')
    String get lastName;
    
        @nullable
    @BuiltValueField(wireName: r'email')
    String get email;
    
        @nullable
    @BuiltValueField(wireName: r'password')
    String get password;
    
        @nullable
    @BuiltValueField(wireName: r'phone')
    String get phone;
    /* User Status */
        @nullable
    @BuiltValueField(wireName: r'userStatus')
    int get userStatus;

    // Boilerplate code needed to wire-up generated code
    User._();

    factory User([updates(UserBuilder b)]) = _$User;
    static Serializer<User> get serializer => _$userSerializer;

}

Expected generated file:

        import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

part 'user.g.dart';

abstract class UserApiModel implements Built<UserApiModel, UserBuilder> {

    ...

    // Boilerplate code needed to wire-up generated code
    UserApiModel._();

    factory UserApiModel([updates(UserApiModelBuilder b)]) = _$UserApiModel;
    static Serializer<UserApiModel> get serializer => _$userApiModelSerializer;

}

It looks like --api-name-suffix and --model-name-suffix are ignored.