Payment and sale model

[ghost]

Both

• Remove the options for delete sales and payment, but there must be an opportunity for negative sales and payments.

Payment model

• Add source to the payment model. (Card, Cash, Bank/Mobile)

[fishbacon]

These seem like two distinct feature requests, please make an enhancement request for each. And please add a bit of motivation.

[fishbacon]

Eh, really no reason to close this and #55. Kindly split up this and #55 into several issues or write a story like #56 to motivate the reason the features should be connected.