Handle API failures when not connected to the internet

[teocomi]

Should probably throw an exception when no internet is available or the API cannot be reached. If the call below fails there is not catch to handle it:

SpeckleCore/SpeckleCore/SpeckleApiClientApiCalls.cs

Line 337 in a8c054a

var response_ = await client_.SendAsync( request_, System.Net.Http.HttpCompletionOption.ResponseHeadersRead, cancellationToken ).ConfigureAwait( false );

[didimitrie]

I would see the easiest way to fix this via an InternetAccess flag which can be checked in the PrepareRequest and execeptions thrown. https://github.com/speckleworks/SpeckleCore/blob/master/SpeckleCore/SpeckleApiClientHead.cs#L58

I'm hesitant to change the autogenerated code, as it will make subsequent future generations more painful. But if nswag can be coerced into adding that catch, i'm fine :)