migration25: export methods to be used for following migrations

This commit exports several private methods to be used in later
migrations. It's safe to do so as no actual logic or migration scheme is
changed.

channeldb/migration25/migration_test.go

@@ -256,7 +256,7 @@ func genBeforeMigration(c *OpenChannel,
 		}
 
 		// Create the channel bucket.
-		chanBucket, err := createChanBucket(tx, c)
+		chanBucket, err := CreateChanBucket(tx, c)
 		if err != nil {
 			return err
 		}
@@ -295,7 +295,7 @@ func genAfterMigration(ourAmt, theirAmt lnwire.MilliSatoshi,
 			return nil
 		}
 
-		chanBucket, err := fetchChanBucket(tx, c)
+		chanBucket, err := FetchChanBucket(tx, c)
 		if err != nil {
 			return err
 		}
@@ -334,42 +334,6 @@ func genAfterMigration(ourAmt, theirAmt lnwire.MilliSatoshi,
 	}
 }
 
-func createChanBucket(tx kvdb.RwTx, c *OpenChannel) (kvdb.RwBucket, error) {
-	// First fetch the top level bucket which stores all data related to
-	// current, active channels.
-	openChanBucket, err := tx.CreateTopLevelBucket(openChannelBucket)
-	if err != nil {
-		return nil, err
-	}
-
-	// Within this top level bucket, fetch the bucket dedicated to storing
-	// open channel data specific to the remote node.
-	nodePub := c.IdentityPub.SerializeCompressed()
-	nodeChanBucket, err := openChanBucket.CreateBucketIfNotExists(nodePub)
-	if err != nil {
-		return nil, err
-	}
-
-	// We'll then recurse down an additional layer in order to fetch the
-	// bucket for this particular chain.
-	chainBucket, err := nodeChanBucket.CreateBucketIfNotExists(
-		c.ChainHash[:],
-	)
-	if err != nil {
-		return nil, err
-	}
-
-	var chanPointBuf bytes.Buffer
-	err = mig.WriteOutpoint(&chanPointBuf, &c.FundingOutpoint)
-	if err != nil {
-		return nil, err
-	}
-
-	// With the bucket for the node fetched, we can now go down another
-	// level, creating the bucket for this channel itself.
-	return chainBucket.CreateBucketIfNotExists(chanPointBuf.Bytes())
-}
-
 // putChannelLogEntryLegacy saves an old format revocation log to the bucket.
 func putChannelLogEntryLegacy(chanBucket kvdb.RwBucket,
 	commit *mig.ChannelCommitment) error {