LN payment flow hardening

[danieldaquino]

This is a placeholder task for further improvements/hardening of the LN payment flow.

Continuation of https://github.com/damus-io/damus/issues/1754 and https://github.com/damus-io/damus/issues/1827

Acceptance criteria

• [x] Add unit tests to damus-api that covers the LN flow as well as edge cases
• [x] Add support@damus.io email on purple website and checkout
• [ ] Lightning flow: Better integrate lightning expiry into the code as a mechanism to prevent stale/unmonitored invoices and improve robustness
• [x] Make sure expiry bumping logic handles edge cases
• [x] Save checkout objects into a DB for better crash resistance
• [ ] Add more timestamps and data to the DBs, as well as server logs to help us diagnose problems and manually fix things in case issues arise
• [ ] LN flow: Handle edge cases better (e.g. How does the UI display an expired invoice? How does the UI handle when the server is having issues? Does it displays errors nicely?)
• [x] Add more guidance on the UI for certain edge cases (e.g. What if the user is running an incompatible version of Damus and the Verify npub link does not work? There should be some message in the website mentioning that if the link fails they might need to update the app)
• [x] Better safeguards against unauthorized use of damus:purple links
• [ ] Add monitoring for oom? issues @jb55 Checkinvoice API codepath status LN node waitinvoice. Call over LNsocket. If issue, send notification.
• [x] Add special endpoint for staging server to allow an account to be reset (for testing purposes)
• On iOS, make "Verify Npub" screen raise a session flag indicating that a checkout is in progress, and detect if account was created when app enters foreground, to show welcome sheet right away Moved to https://github.com/damus-io/damus/issues/2021

Note: This ticket is generic, it can be split into more tickets if convenient.

[danieldaquino]

@jb55, since the recent damus-api changes might still be fresh in your mind, what do you think of the acceptance criteria here? Any other suggestions on things we can do to improve robustness?

To save you a trip to Github, I will list them here so you can stay in your email client lol:

• Add unit tests to damus-api that covers the LN flow as well as edge cases
• Add support@damus.io email on purple website and checkout
• Lightning flow: Better integrate lightning expiry into the code as a mechanism to prevent stale/unmonitored invoices and improve robustness
• Make sure expiry bumping logic handles edge cases
• Save checkout objects into lmdb for better crash resistance
• Add more timestamps and data to the DBs, as well as server logs to help us diagnose problems and manually fix things in case issues arise
• LN flow: Handle edge cases better (e.g. How does the UI display an expired invoice? How does the UI handle when the server is having issues? Does it displays errors nicely?)
• Add more guidance messages on the UI for certain edge cases (e.g. What if the user is running an incompatible version of Damus and the Verify npub link does not work? There should be some message in the website mentioning that if the link fails they might need to update the app)
• Better safeguards against unauthorized use of damus:purple links

[danieldaquino]

Save checkout objects into a DB for better crash resistance

Patch sent: https://groups.google.com/a/damus.io/g/patches/c/eT2BINfOH0Q

[danieldaquino]

@jb55, @alltheseas, I wrote some code to better handle checkout errors (if they occur)

I went on each function, each step of the checkout process, and added error handlers with a detailed message.

• Each message contains tailored action tips for the user on what to do if they encounter such error
• The popup shows the user info on how to contact support
• The popup gives users the checkout reference code that they can copy and save, to facilitate troubleshooting for us

Here is one example:

[danieldaquino]

@jb55, don't know if this is the right ticket to send this, but here is a preview of the discount label I just wrote (I did not send this patch yet)

[alltheseas]

Figure out which are critical items

[alltheseas]

What should expiry invoice duration be? @danieldaquino suggests short invoice, so LN node does not have to keep checking status for invoices.

Core LN default is one (1) week.

There remains one unsolved checkout/subscription request.

[danieldaquino]

On iOS, make "Verify Npub" screen raise a session flag indicating that a checkout is in progress, and detect if account was created when app enters foreground, to show welcome sheet right away

Moved this to https://github.com/damus-io/damus/issues/2021