Add support for AMP LN invoices [Feature Request][UX]

[alltheseas]

User Story

As an advanced Damus & LN user who is looking to send more sats over LN + increase my privacy + increase my chance of a successful zap, I want the ability to generate atomic multi-path LN payments (AMP) invoices, so that I have the option to send larger payments over LN, improve my privacy, and improve my chance of a successful zap.

Acceptance Criteria

1. User can place AMP LN invoices identifier in BITCOIN LIGHTNING TIPS field in edit profile view
2. LN invoice defaults to AMP LN

Questions How might Damus handle the situation where a particular LN user/wallet does not support AMP invoices?

Reference & resources https://docs.lightning.engineering/lightning-network-tools/lnd/amp

"no need to rely on a 3rd party custodial wallets by allowing amp invoices instead of lud-06 lightning addresses."

https://thebitcoinmanual.com/articles/atomic-multi-path-payments/

Claims to

"reduces the chances of failed payments and improves the user experience of Lightning. It allows for larger transactions to be conducted on Lightning and takes even more strain on the base layer, driving down the cost of block space in theory. "

Corollary:

"While in the absence of AMP, the user will always have a capped base limit on how much they can send despite having more money in the wallet, which can be a wired experience for the user. Consider having 100 [satoshis](https://thebitcoinmanual.com/btc-culture/glossary/satoshi-2/) in the account, but you can only send 20 satoshis because the payment channels don’t support 100 satoshis!"

https://youtu.be/PNSPXRflCSc

https://lightning.engineering/posts/2021-06-17-lnd-v0.13/

https://bitcoin.stackexchange.com/questions/89475/what-are-atomic-multi-path-payments-amps-and-why-how-is-it-being-implemented-i/89476#89476

https://github.com/lightning/bolts/pull/658

https://github.com/lightningnetwork/lnd/blob/master/docs/release-notes/release-notes-0.14.0.md#re-usable-static-amp-invoices

Origin: @kortik7 https://github.com/damus-io/damus/issues/477#issuecomment-1413037293

[alltheseas]

Objections

@Semisol mentions "AMP is not compatible with other implementations, BOLT12 has support from 2 implementations and is way more flexible and better standardized."

https://damus.io/note18mrl4g2tkexteh3cnvyy8zv94jsx6k2hyn8fs74fgqltjw2u9f9sqny94y