✨ (backend) Mail when installment debit has failed

[jonathanreveille]

Purpose

This PR will solve this issue When an installment debit has failed, we need to inform the user with an email about the failed payment.

Proposal

• [x] Create MJML template email when an installment is refused
• [x] Create debug view for our fellow developers to see the layout and how is rendered the email sent to the user
• [x] Adjust logic in base payment backend when installment payment fails