Now that the checkbox is hidden behind an advanced option, there is
no need to be brief about it, better to be explicit.
(terminology unchanged for kivy.)
- trampoline is enabled by default in config, to prevent download of `gossip_db`.
(if disabled, `gossip_db` will be downloaded, regardless of the existence of channels)
- if trampoline is enabled:
- the wallet can only open channels with trampoline nodes
- already-existing channels with non-trampoline nodes are frozen for sending.
- there are two types of trampoline payments: legacy and end-to-end (e2e).
- we decide to perform legacy or e2e based on the invoice:
- we use trampoline_routing_opt in features to detect Eclair and Phoenix invoices
- we use trampoline_routing_hints to detect Electrum invoices
- when trying a legacy payment, we add a second trampoline to the path to preserve privacy.
(we fall back to a single trampoline if the payment fails for all trampolines)
- the trampoline list is hardcoded, it will remain so until `trampoline_routing_opt` feature flag is in INIT.
- there are currently only two nodes in the hardcoded list, it would be nice to have more.
- similar to Phoenix, we find the fee/cltv by trial-and-error.
- if there is a second trampoline in the path, we use the same fee for both.
- the final spec should add fee info in error messages, so we will be able to fine-tune fees
- LNWorker is notified about htlc events and creates payment events.
- LNWorker._pay is a while loop that calls create_routes_from_invoice.
- create_route_from_invoices should decide whether to split the payment,
using graph knowledge and feedback from previous attempts (not in this commit)
- data structures for payment logs are simplified into a single type, HtlcLog
Main motivation is that I often use wallet.remove_transaction
from the Qt console, and would find this behaviour more intuitive.
Note that previously if one were to call this on a tx with children,
the crash reporter would appear with "wallet.get_history() failed balance sanity-check".
related: https://github.com/spesmilo/electrum/issues/6960#issuecomment-764716533
