[New Feature] Razorpay integration and Newsletter to participants

[wisharya]

New feature request

Abhinav (@abhinavxd) is volunteering for this feature.

1. Create an email group for each conference.
2. Get the email address from the Razorpay dashboard to the email group.
   1. We need to put the Razorpay page id in the conference doctype.
3. Create a Table for sending newsletters/notifications to the participants with the following fields
   1. Subject
   2. Body
   3. Send Button
   4. Timestamp
   5. Status: Draft, Queue, Finished
4. Feedback form for each conference.

We need to add a custom field reply-to for all the newsletters for the reply email from the participants. Eg: We have an email group [email protected] for DelhiFOSS. This email needs to be added in the reply-to field in the conference doctype.