Expose version information in the orchestration context

It would be convenient if orchestration instances could know their versions so that developers could write inline branch logic when versioning their orchestrations rather than mapping new versions to new classes, which is a bit more heavy-handed.

This is something supported by Temporal: https://docs.temporal.io/docs/go-versioning/. I think it would be useful to have in DTFx as well, though developers would need to use it carefully.

Example:

    class LongRunningOrchestration : TaskOrchestration<string, string>
    {
        public override async Task<string> RunTask(OrchestrationContext context, string input)
        {
            await context.ScheduleTask<string>(typeof(ActivityA), input);

            // At this point in the orchestration, a change may have been deployed

            if (context.Version == Version1)
            {
                await context.ScheduleTask<object>(typeof(ActivityB1), input);
            }
            else if (context.Version == Version2)
            {
                await context.ScheduleTask<object>(typeof(ActivityB2), input);
            }

            return $"Completed as version '{context.Version}'";
        }
    }

[jviau]

@cgillum thanks! I might open a different issue to discuss this problem and how DTFx could improve upon it.

[jviau]

I solved this in our codebase by having Name and Version be properties on our base class OrchestrationBase. And then middleware sets it, as the name and version are available there via DispatchMiddlewareContext.GetProperty<OrchestrationRuntimeState>(). Did a similar approach for Activities - just a different property to get from the middleware context.