BUG : Stripe minimum order amount

[tomik-z-cech]

Describe the bug :
Stripe payment intent cannot be created if the amount to charge is < 0.50 €.

To Reproduce :

• Navigate to shop
• Navigate to any item that has price per unit less than 50c.
• Navigate to Vault
• Navigate to Secure Checkout from Vault
• See terminal for error message

Expected behavior :
All payment intents are sucessfully created.

Screenshots :

Devices :
All devices.

Additional context :
Minimum order amount needs to be created and applied in Checkout logic.

[tomik-z-cech]

Minimum order value added to postage settings model and line elif subtotal < postage_settings.minimum_order: added to checkout views.py.

Bug fixed in commit e4af873.