[JAVA][library: vertx] generated client does not maintain backwards compatibility with older versions of vertx

Description

The buildResponseHandler method defined in Java/libraries/vertx/ApiClient.mustache makes a call to Json.decodeValue(String, Class<T>) which is not supported in older versions (< 3.5) of Vert.x. The call should be adjusted to handle all versions.

Swagger-codegen version

All versions with vertx async & rx support

Suggest a fix/enhancement

Change the call from:

resultContent = Json.decodeValue(httpResponse.body(), returnType);

to:

try {
   resultContent = Json.mapper.readValue(httpResponse.bodyAsString(), returnType);
} catch (Exception e) {
   throw new DecodeException("Failed to decode:" + e.getMessage(), e);
}

Start in Java/libraries/vertx/ApiClient.mustache and inspect the buildResponseHandler method and its response-decoding path. Check how generated clients handle Vert.x versions below 3.5, then verify that generated Vert.x clients retain compatibility with those versions and that decoding failures remain represented by the expected exception.