Description

This PR contains the following changes:

1. Migrated StripeDecimalCurrencyAmountField to StripeQuantumCurrencyAmountField for the following models:

   • Source
   • SourceTransaction
   • Transfer
   • Coupon
   • BaseInvoice
   • InvoiceItem
   • Plan
   • Payout
   • Charge

2. Updated Coupon.human_readable_amount to correctly fetch and display (in cents) the Integral amount_off model field.

3. Updated Plan. human_readable_price to correctly fetch and display (in cents) the Integral unit_amount model field.

4. Updated Plan. create to correctly fetch and display (in cents) the Integral amount model field.

5. Updated Price. create to correctly fetch and display (in cents) the Integral unit_amount model field.

6. Updated Charge._calculate_refund_amount to correctly fetch and display (in cents) the Integral amount_to_refund model field.

7. Updated Charge.charge to correctly fetch and display (in cents) the Integral amount and application_fee model fields.

8. Updated Charge.add_invoice_item to correctly fetch and display (in cents) the Integral amount model field.

9. Removed unnecessary Plan.amount_in_cents model property.

10. Updated Corresponding Tests.

Checklist:

• I've updated the tests or confirm that my change doesn't require any updates.
• I've updated the documentation or confirm that my change doesn't require any updates.
• I confirm that my change doesn't drop code coverage below the current level.
• I've updated migrations or confirm that my change doesn't make changes to any model.

Rationale

Fix: #955
Fix: #1941
Brings us one step closer to reducing the usage of the legacy StripeDecimalCurrencyAmountField