lnworker: differentiate PaymentInfo by direction

Allows storing two different payment info of the same payment hash by
including the direction into the db key.
We create and store PaymentInfo for sending attempts and for requests (receiving),
if we try to pay ourself (e.g. through a channel rebalance) the checks
in `save_payment_info` would prevent this and throw an exception.
By storing the PaymentInfos of outgoing and incoming payments separately in
the db this collision is avoided and it makes it easier to reason about
which PaymentInfo belongs where.

electrum/wallet_db.py

@@ -69,7 +69,7 @@ class WalletUnfinished(WalletFileException):
 # seed_version is now used for the version of the wallet file
 OLD_SEED_VERSION = 4        # electrum versions < 2.0
 NEW_SEED_VERSION = 11       # electrum versions >= 2.0
-FINAL_SEED_VERSION = 63     # electrum >= 2.7 will set this to prevent
+FINAL_SEED_VERSION = 64     # electrum >= 2.7 will set this to prevent
                             # old versions from overwriting new format
 
 
@@ -235,6 +235,7 @@ class WalletDBUpgrader(Logger):
         self._convert_version_61()
         self._convert_version_62()
         self._convert_version_63()
+        self._convert_version_64()
         self.put('seed_version', FINAL_SEED_VERSION)  # just to be sure
 
     def _convert_wallet_type(self):
@@ -1269,6 +1270,24 @@ class WalletDBUpgrader(Logger):
 
         self.data['seed_version'] = 63
 
+    def _convert_version_64(self):
+        """Key payment_info by "rhash:direction" instead of just rhash to allow storing a PaymentInfo
+        for each direction"""
+        if not self._is_upgrade_method_needed(63, 63):
+            return
+
+        new_payment_infos = {}
+        old_payment_infos = self.data.get('lightning_payments', {})
+        for payment_hash, old_values in old_payment_infos.items():
+            amount_msat, direction, status, min_final_cltv_expiry, expiry, creation_ts = old_values
+            # drop direction
+            new_values = (amount_msat, status, min_final_cltv_expiry, expiry, creation_ts)
+            new_key = f"{payment_hash}:{direction}"
+            new_payment_infos[new_key] = new_values  # save new entry
+
+        self.data['lightning_payments'] = new_payment_infos
+        self.data['seed_version'] = 64
+
     def _convert_imported(self):
         if not self._is_upgrade_method_needed(0, 13):
             return