Add option to ASP.NET Core to flush events after response complete

[bruno-garcia]

This feature will resolve issue #126. See this comment for details.

Add an option to SentryAspNetCoreOptions named FlushOnCompletedRequest of type bool and a FlushTimeout with default value of Timestamp.FromSeconds(2).

Inside SentryMiddleware, check for this flag in the options and if opt in, add to context.Response.OnCompletd like the snippet from @madmox in #126:

context.Response.OnCompleted(async () =>
{
      await sentryClient.FlushAsync(timeout: _options.FlushTimeout);
});

await this._next(context);

Tests are required to assert FlushAsync isn't called by default and when the flag is set to false. And otherwise it is called with the default Timeout. Modifying the timeout should affect the parameter passed to FlushAsync.

[bruno-garcia]

This was resolved already a year ago :X