ASPA-27/Integrate PoliPay as a replacement for bank transfer

[victor-gan]

Issue:
Need polipay

Solution:

• Enabled Polipay button on payment method page
• Created a function that is called when the proceed payment button is clicked in enrollmentform.php
• Created PolipayModel.php

Risk:
[Enter any potential risks identified here]

Reviewed By:
[Edit the message as to who reviewed it here]