Unclear exception when calling TerminateInstanceAsync on invalid instance

[andystaples]

Description

When calling TerminateInstanceAsync() in dotnet-isolated on an orchestration ID that is already completed, terminated, or otherwise not eligable for termination, you get an RpcException with the following message:
Status(StatusCode="Unknown", Detail="Exception was thrown by handler.")
This is unhelpful and we are losing the detail provided by the exception thrown here:

azure-functions-durable-extension/src/WebJobs.Extensions.DurableTask/ContextImplementations/DurableClient.cs

Line 399 in 3bfd149

throw new InvalidOperationException($"Cannot terminate the orchestration instance {instanceId} because instance is in the {state.OrchestrationStatus} state.");

Expected behavior

Terminating an invalid orchestration should throw an exception with a helpful stack trace and error message.

Actual behavior

Terminating a scheduled orchestration throws a generic RpcException.

Relevant source code snippets

        [Function("TerminateInstance")]
        public static async Task<HttpResponseData> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req,
            [DurableClient] DurableTaskClient client,
            string instanceId)
        {
            string reason = "Long-running orchestration was terminated early.";
            try 
            {
                await client.TerminateInstanceAsync(instanceId, reason);
                return req.CreateResponse(HttpStatusCode.OK);
            }
            catch (RpcException ex) 
            {
                var response = req.CreateResponse(HttpStatusCode.BadRequest);
                response.Headers.Add("Content-Type", "text/plain");
                await response.WriteStringAsync(ex.Message);
                return response;
            }
        }

Known workarounds

None

App Details

Latest Durable worker extension **1.2.2/dotnet-isolated/FunctionsV4