[REQ] add getWebClient to ApiClient

Created by: PeterBuschSF

Describe the solution you'd like

My company uses spring-cloud-sleuth for transaction tracing. This tool requires that the WebClient be registered as a Bean.

I would prefer to allow the ApiClient to build the WebClient using it's defaults. Then retrieve the completed WebClient from the ApiClient so I can register as a Bean.

ApiClient apiClient = new ApiCient();
WebClient webClient = apiClient.getWebClient();

Describe alternatives you've considered

I currently achieve this by:

1. Create an ObjectMapper using the steps copied from from the ApiClient's default constructor.
2. Call ApiClient.buildWebClient with the ObjectMapper to build the WebClient
3. Call the ApiClient(WebClient, ObjectMapper, DateFormat) constructor to build the ApiClient object.

I realize if I needed to customize the ObjectMapper, DateFormat, and/or WebClient, I might use this option anyway. But I don't have a need for that.