Create a new budget for a model and wallet.

        @param the name of the wallet.
        @param the model UUID.
        @param the new value of the limit.
        @return a success string from the plans server.
        @raise ServerError via make_request.

def create_budget(self, wallet_name, model_uuid, limit):
        """Create a new budget for a model and wallet.

        @param the name of the wallet.
        @param the model UUID.
        @param the new value of the limit.
        @return a success string from the plans server.
        @raise ServerError via make_request.
        """
        request = {
            'model': model_uuid,
            'limit': limit,
        }
        return make_request(
            '{}wallet/{}/budget'.format(self.url, wallet_name),
            method='POST',
            body=request,
            timeout=self.timeout,
            client=self._client)