All the stuff you have so far looks good, but we need a way to handle the 2 different inputs, 'Approve' or 'Deny'
You should look up stuff for using multiple submit buttons in forms, but the general idea is to rewrite form_valid with something like this:
    def form_valid(self, form):
        if '_approve' in self.request.POST:
            # do approval stuff
        elif '_deny' in self.request.POST:
            # do deny stuff

You also need to add corresponding 'name' attributes to your input buttons in your template for this to work. In this example, the names '_approve' and '_deny', which lets us know which button the user clicked