Project: Payment Gateway Integration (Tested only for payUMoney)
Author: Vikas Tuteja
Date: 11 Nov, 2017

PREREQUISITES
 * django 1.6 or above
 * drf 3.6.1 or above


INSTALLING
 * copy the paymentgateway folder in your Base directory
 * include paymentgateway in your installed apps settings
 * activate your virtualenv
 * ./paymentgateway/setup


OVERVIEW
 * This package is used to integrate the payment gateway with your django application.
 * P.S: It supports payUMoney as of now, can be evolved to work with other payment gateways.

 * MODELS
    1. Configuration - Contains the payment gateway service provider's basic configuration- merchant name, key, success & failure urls, etc
    2. Transaction Request - All the transaction requests sent to the payment gateway are stored here.
    3. Transaction Response - All the transaction response received from the payment gateway must be saved in this model.

 * API's
    1. Url: /paymentgateway/transactionrequest/add/?format=json
       method: POST
       Usage: This API should be called before a user is redirected to the payUMoney website.
              It will create a transaction request object, along with the required hash key and unique txn id.
              A list of form inputs needs to be sent to this API as well as the payment gateway in order to initate the transaction.

       refer sample input form template - paymentgateway/templates/sampleinputform.html


    2. Url: /paymentgateway/transactionresponse/<status>/ - where status can be success/failure
       method: GET
       Usage: This is a callback API used by payUmoney to redirect the user back to our website after the payment process.
              It saves an object of the response sent by payUMoney against its OneToOne mapping of the unique transaction id.

       sample response url: http://your_website.com/paymentgateway/transactionresponse/success/?txnid=b9404169e3bf33c46f509596cdc152&status=Completed&
       payuMoneyId=asd&hash=b12ddb717e03bcec420b23395396b0d00ab709eb568757d29a832d24414e0373a7c8ecd76b922953b8764fd4fe0529289ce2e0362eba8292033d4s&
       mode=CC&firstname=Vikas&amount=100.00&phone=9146166344&email=vikas.tuteja4@hindustantimes.com&productinfo=xyz&payuMoneyId=123qwe&format=json

       sample response template - paymentgateway/templates/pay_response.html

    P.S: both API's return a json response


ADDITIONAL FEATURE
 * You may map each transaction request to payU with any entity of your application, by simply passing the following 2 params to the transaction add API:-
    content_type - which is an id of your model and
    object id - which is the id of the object to which a transaction needs to be mapped.