feat: drop send() function so we handle redirects better

Sometimes when dealing with redirects, python requests calls self.send() multiple times for each redirect, and this is frustrating since all the original code I had modified the response after sending, so instead, move this to a new function called _response_handler() and put this function in self.request() instead. That should handle the "callback" better by only running it on the final returned response, rather than intermediate responses.