Improve handling of lightning payment status:

- Move 'handle_error_code_from_failed_htlc' to channel_db,
and call it from pay_to_route, because it should not be
called when HTLCs are forwarded.
- Replace 'payment_received' and 'payment_status'
callbacks with 'invoice_status' and 'request_status'.
- Show payment error logs in the Qt GUI
- In the invoices list, show paid invoices for which
we still have the log.

electrum/channel_db.py

@@ -39,6 +39,8 @@ from .util import bh2u, profiler, get_headers_dir, bfh, is_ip_address, list_enab
 from .logging import Logger
 from .lnutil import LN_GLOBAL_FEATURES_KNOWN_SET, LNPeerAddr, format_short_channel_id, ShortChannelID
 from .lnverifier import LNChannelVerifier, verify_sig_for_channel_update
+from .lnonion import OnionFailureCode
+from .lnmsg import decode_msg
 
 if TYPE_CHECKING:
     from .network import Network
@@ -385,6 +387,57 @@ class ChannelDB(SqlDB):
         # the update may be categorized as deprecated because of caching
         categorized_chan_upds = self.add_channel_updates([payload], verify=False)
 
+    def handle_error_code_from_failed_htlc(self, code, data, sender_idx, route):
+        # handle some specific error codes
+        failure_codes = {
+            OnionFailureCode.TEMPORARY_CHANNEL_FAILURE: 0,
+            OnionFailureCode.AMOUNT_BELOW_MINIMUM: 8,
+            OnionFailureCode.FEE_INSUFFICIENT: 8,
+            OnionFailureCode.INCORRECT_CLTV_EXPIRY: 4,
+            OnionFailureCode.EXPIRY_TOO_SOON: 0,
+            OnionFailureCode.CHANNEL_DISABLED: 2,
+        }
+        if code in failure_codes:
+            offset = failure_codes[code]
+            channel_update_len = int.from_bytes(data[offset:offset+2], byteorder="big")
+            channel_update_as_received = data[offset+2: offset+2+channel_update_len]
+            channel_update_typed = (258).to_bytes(length=2, byteorder="big") + channel_update_as_received
+            # note: some nodes put channel updates in error msgs with the leading msg_type already there.
+            #       we try decoding both ways here.
+            try:
+                message_type, payload = decode_msg(channel_update_typed)
+                payload['raw'] = channel_update_typed
+            except:  # FIXME: too broad
+                message_type, payload = decode_msg(channel_update_as_received)
+                payload['raw'] = channel_update_as_received
+            categorized_chan_upds = self.add_channel_updates([payload])
+            blacklist = False
+            if categorized_chan_upds.good:
+                self.logger.info("applied channel update on our db")
+                #self.maybe_save_remote_update(payload)
+            elif categorized_chan_upds.orphaned:
+                # maybe it is a private channel (and data in invoice was outdated)
+                self.logger.info("maybe channel update is for private channel?")
+                start_node_id = route[sender_idx].node_id
+                self.add_channel_update_for_private_channel(payload, start_node_id)
+            elif categorized_chan_upds.expired:
+                blacklist = True
+            elif categorized_chan_upds.deprecated:
+                self.logger.info(f'channel update is not more recent.')
+                blacklist = True
+        else:
+            blacklist = True
+        if blacklist:
+            # blacklist channel after reporter node
+            # TODO this should depend on the error (even more granularity)
+            # also, we need finer blacklisting (directed edges; nodes)
+            try:
+                short_chan_id = route[sender_idx + 1].short_channel_id
+            except IndexError:
+                self.logger.info("payment destination reported error")
+            else:
+                self.network.path_finder.add_to_blacklist(short_chan_id)
+
     def create_database(self):
         c = self.conn.cursor()
         c.execute(create_node_info)