Add multiple payment methods while lending

[nirzaf]

Fixes #166

Add support for multiple payment methods in loan applications and loans.

• Add a new doctype Payment Method Limit to define the cash limit.
• Update loan_application.js to include a payment section with multiple modes of payment.
  • Add validation to check if the cash limit is obeyed.
  • Show an error screen if the cash limit is exceeded and auto-update the entered lending value for cash to 20,000.
• Update loan_application.py to handle the logic for multiple payment methods.
  • Add logic to distribute the remaining amount to other payment methods like bank transfer or UPI.
• Update loan.js to support multiple payment methods.
  • Add a payment section with multiple modes of payment.
  • Add validation to check if the cash limit is obeyed.
  • Show an error screen if the cash limit is exceeded and auto-update the entered lending value for cash to 20,000.
• Update loan.py to handle the logic for multiple payment methods.
  • Add logic to distribute the remaining amount to other payment methods like bank transfer or UPI.