Communication with OpenNode #17
Description
When user press the "Generate Invoice" button, the application should communicate with OpenNode (https://api.opennode.co/v1/charges) to create an invoice.
OpenNode will return a LN invoice and an on-chain address. The QRcode for the LN invoice should be shown. A button could be created later for showing the on-chain address.
A button should allow the user to copy the LN invoice (payreq) or the on-chain address to the clipboard (for sharing via Telegram, for example).
The application should check once per second (using https://api.opennode.co/v1/charge/id) and wait until the payment is made.
A button should allow cancelling.
When the payment is made, show message with relevant information to notify the user. This message should not disappear without user interaction (like pressing an OK button).