sqldb: add SQLStrValid helper

The SQL* helpers are meant to always set the `Valid` field of the
sql.Null* type to true. Otherwise they cannot be used to set a valid,
empty field. However, we dont want to break the behaviour of the
existing SQLStr helper and so this commit adds a new helper with the
desired functionality.

graph/db/sql_migration.go

@@ -1380,8 +1380,8 @@ func insertNodeSQLMig(ctx context.Context, db SQLQueries,
 
 	if node.HaveNodeAnnouncement {
 		params.LastUpdate = sqldb.SQLInt64(node.LastUpdate.Unix())
-		params.Color = sqldb.SQLStr(EncodeHexColor(node.Color))
-		params.Alias = sqldb.SQLStr(node.Alias)
+		params.Color = sqldb.SQLStrValid(EncodeHexColor(node.Color))
+		params.Alias = sqldb.SQLStrValid(node.Alias)
 		params.Signature = node.AuthSigBytes
 	}
 

graph/db/sql_store.go

@@ -3391,8 +3391,8 @@ func upsertNode(ctx context.Context, db SQLQueries,
 
 	if node.HaveNodeAnnouncement {
 		params.LastUpdate = sqldb.SQLInt64(node.LastUpdate.Unix())
-		params.Color = sqldb.SQLStr(EncodeHexColor(node.Color))
-		params.Alias = sqldb.SQLStr(node.Alias)
+		params.Color = sqldb.SQLStrValid(EncodeHexColor(node.Color))
+		params.Alias = sqldb.SQLStrValid(node.Alias)
 		params.Signature = node.AuthSigBytes
 	}