Add payments as a payment option entering manual payment on invoice

[TekWarren]

What version of Invoice Ninja are you running? v5

What environment are you running?
Docker

Additional context
The payment screen for invoices is missing the option to apply an existing, partially applied payment. Instead to use a bulk payment, you have to create the invoice and then go to the payments, find the clients bulk or overpayment, and then apply it open invoices. It would be much more convenient to just have this as an option on the "enter payment" screen of an invoice as we currently have the option to choose from credits, other invoices, or manual entry.

This stems from the inability to have payments behind credits (separate request)