lnrater: don't suggest nodes we have a channel backup with

We don't want to connect to nodes we already have a channel with on another device.

electrum/lnchannel.py

@@ -59,7 +59,7 @@ from .lnhtlc import HTLCManager
 from .lnmsg import encode_msg, decode_msg
 from .address_synchronizer import TX_HEIGHT_LOCAL
 from .lnutil import CHANNEL_OPENING_TIMEOUT
-from .lnutil import ChannelBackupStorage, ImportedChannelBackupStorage
+from .lnutil import ChannelBackupStorage, ImportedChannelBackupStorage, OnchainChannelBackupStorage
 from .lnutil import format_short_channel_id
 
 if TYPE_CHECKING:
@@ -148,7 +148,7 @@ class AbstractChannel(Logger, ABC):
     _fallback_sweep_address: str
     channel_id: bytes
     funding_outpoint: Outpoint
-    node_id: bytes
+    node_id: bytes  # note that it might not be the full 33 bytes; for OCB it is only the prefix
     _state: ChannelState
 
     def set_short_channel_id(self, short_id: ShortChannelID) -> None:
@@ -391,6 +391,11 @@ class AbstractChannel(Logger, ABC):
     def is_static_remotekey_enabled(self) -> bool:
         pass
 
+    @abstractmethod
+    def get_local_pubkey(self) -> bytes:
+        """Returns our node ID."""
+        pass
+
 
 class ChannelBackup(AbstractChannel):
     """
@@ -513,6 +518,14 @@ class ChannelBackup(AbstractChannel):
         # their local config is not static)
         return False
 
+    def get_local_pubkey(self) -> bytes:
+        cb = self.cb
+        assert isinstance(cb, ChannelBackupStorage)
+        if isinstance(cb, ImportedChannelBackupStorage):
+            return ecc.ECPrivkey(cb.privkey).get_public_key_bytes(compressed=True)
+        if isinstance(cb, OnchainChannelBackupStorage):
+            return self.lnworker.node_keypair.pubkey
+        raise NotImplementedError(f"unexpected cb type: {type(cb)}")
 
 
 class Channel(AbstractChannel):