fix: getting first available content type for parametersV2 method

[elenaferr0]

I added another check in the parametersV2 method so that if there is a content type which is not multipart or form url encoded it is added to the request. For example, I would expect the following swagger:

{
  "swagger": "2.0",
  "info": {
    "description": "",
    "version": "",
    "title": "Test swagger"
  },
  "host": "localhost:8081",
  "basePath": "/",
  "tags": [
    {
      "name": "Tests",
      "description": "Test Controller"
    }
  ],
  "paths": {
    "/test": {
      "patch": {
        "tags": [
          "Tests"
        ],
        "description": "Description",
        "operationId": "operationId",
        "consumes": [
          "application/json-patch+json"
        ],
        "produces": [
          "application/json"
        ],
        "parameters": [],
        "responses": {
          "200": {
            "description": "Success"
          }
        }
      }
    }
  },
  "definitions": {}
}

to generate the following dart code:

@RestApi()
abstract class TestsClient {
  factory TestsClient(Dio dio, {String? baseUrl}) = _TestsClient;

  /// Description
  @Headers(<String, String>{'Content-Type': 'application/json-patch+json'})
  @PATCH('/test')
  Future<void> operationId();
}

But instead generates this (the @Headers annotation is missing):

@RestApi()
abstract class TestsClient {
  factory TestsClient(Dio dio, {String? baseUrl}) = _TestsClient;

  /// Description
  @PATCH('/test')
  Future<void> operationId();
}

I also fixed the parser request_tests for v2 (callingactualRestClient.last in that scenario always returns the same element, therefore not all the list element were properly compared). The basic paths check 3.0 test has the same issue, if you switch from

expect(actualRestClients.last, expectedRestClients.last);

to

expect(actualRestClients[i], expectedRestClients[i]);

the test fails, it seems that the returnType is different but I didn't manage to understand why.