Default constructor for the SDK RestClient?

I would like to use the Tessitura.Service.RestClient class in my .NetCore application, but there is no default constructor so I can't inject it as a dependency.  Also, as of v15.1.3, the source code is no longer available so I can't create my own constructor.  

This is the signature that I would like for the RestClient class: `public RestClient(HttpClient client)`  That way I could register it like this: `services.AddHttpClient<IRestClient, RestClient>();` (The Microsoft AddHttpClient extension method uses `HttpClientFactory` to create the httpClient instance instead of using the (no longer recommended) `new HttpClient()` to create a singleton.)  Once RestClient is registered, then the Tessitura services that depend on it can be registered, for example, `services.AddScoped<ITxnRepository, TxnRepository>();` without any dependency issues.  

Is anyone using the SDK in a .NetCore app?  If so, what does your architecture look like, and how are you dealing with dependency injection?  Am I missing something obvious?  Thanks!