Invoices without an amount/with zero amount should be supported.

[data-retriever]

Describe the problem/bug Invoices without an amount/with zero amount should be supported.

Your environment

• Version of ThunderHub: 0.13.16

To Reproduce For invoice creation:

• Click on Receive on lightning section
• Try to press 0 key on Amount to receive or just leave it blank
• Try to Create Invoice

For invoice payment:

• Create a invoice with lncli addinvoice
• Click on Send on lightning section and paste the payment_request on Request
• Try changing the Value field of the decoded invoice

Expected behavior For invoice creation:

• Pressing 0 on the Amount field should be accepted

For invoice payment:

• Editing the Value or some prompt should allow the user to specify the amount to be paid

Actual behavior For invoice creation:

• Create Invoice is only active if Amount to receive > 0

For invoice payment:

• User is unable to edit value and clicking on Pay will generate a UnexpectedPaymentError. amount must be specified when paying a zero amount invoice

Additional context Sometimes I want to receive a payment but I don't know exactly how much the payer should pay me. For instance, If the payer will charge me the estimated lightning fee (to avoid certain attacks where the receiver creates a expensive route to defraud the sender), then the best would just to generate a invoice with a zero value and let him do all the math. The same logic applies if I'm the one that will pay such invoice.

[RajGoodF]

Yes actively looking for this feature