multi: add ToChannelAnnouncement helper on ChannelEdgeInfo

So that we have one place that converts from our `models` struct to the
`lnwire.ChannelAnnouncement` struct.

The commit also refactors netann.CreateChanAnnouncement to only take a
ChannelEdgeInfo and get the proof from there instead of needing the
proof to be passed in separately.

Add ToChannelAnnouncement() method to ChannelEdgeInfo that converts
the model struct to a lnwire.ChannelAnnouncement1 message. This:

- Centralizes the conversion logic in one place instead of scattered
  across multiple call sites
- Validates that AuthProof is present (can't create announcement
  without proof)
- Currently only supports v1 channels, returning error for v2

Refactor netann.CreateChanAnnouncement to use this helper and remove
the separate chanProof parameter since proof is now accessed from
within ChannelEdgeInfo. This improves encapsulation and reduces
parameter count.

netann/channel_announcement.go

@@ -34,48 +34,14 @@ const (
 // function is used to transform out database structs into the corresponding wire
 // structs for announcing new channels to other peers, or simply syncing up a
 // peer's initial routing table upon connect.
-func CreateChanAnnouncement(chanProof *models.ChannelAuthProof,
-	chanInfo *models.ChannelEdgeInfo,
+func CreateChanAnnouncement(chanInfo *models.ChannelEdgeInfo,
 	e1, e2 *models.ChannelEdgePolicy) (*lnwire.ChannelAnnouncement1,
 	*lnwire.ChannelUpdate1, *lnwire.ChannelUpdate1, error) {
 
 	// First, using the parameters of the channel, along with the channel
-	// authentication chanProof, we'll create re-create the original
+	// authentication proof, we'll create re-create the original
 	// authenticated channel announcement.
-	chanID := lnwire.NewShortChanIDFromInt(chanInfo.ChannelID)
-	chanAnn := &lnwire.ChannelAnnouncement1{
-		ShortChannelID:  chanID,
-		NodeID1:         chanInfo.NodeKey1Bytes,
-		NodeID2:         chanInfo.NodeKey2Bytes,
-		ChainHash:       chanInfo.ChainHash,
-		BitcoinKey1:     chanInfo.BitcoinKey1Bytes,
-		BitcoinKey2:     chanInfo.BitcoinKey2Bytes,
-		Features:        chanInfo.Features.RawFeatureVector,
-		ExtraOpaqueData: chanInfo.ExtraOpaqueData,
-	}
-
-	var err error
-	chanAnn.BitcoinSig1, err = lnwire.NewSigFromECDSARawSignature(
-		chanProof.BitcoinSig1(),
-	)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	chanAnn.BitcoinSig2, err = lnwire.NewSigFromECDSARawSignature(
-		chanProof.BitcoinSig2(),
-	)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	chanAnn.NodeSig1, err = lnwire.NewSigFromECDSARawSignature(
-		chanProof.NodeSig1(),
-	)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	chanAnn.NodeSig2, err = lnwire.NewSigFromECDSARawSignature(
-		chanProof.NodeSig2(),
-	)
+	chanAnn, err := chanInfo.ToChannelAnnouncement()
 	if err != nil {
 		return nil, nil, nil, err
 	}

netann/channel_announcement_test.go

@@ -59,9 +59,7 @@ func TestCreateChanAnnouncement(t *testing.T) {
 		models.WithFeatures(features),
 	)
 	require.NoError(t, err)
-	chanAnn, _, _, err := CreateChanAnnouncement(
-		chanProof, chanInfo, nil, nil,
-	)
+	chanAnn, _, _, err := CreateChanAnnouncement(chanInfo, nil, nil)
 	require.NoError(t, err, "unable to create channel announcement")
 
 	assert.Equal(t, chanAnn, expChanAnn)