Preserve column properties on add CHECK constraint operation (#236)

Preserve properties of columns when duplicating them for backfilling to
add a`CHECK` constraint. Currently, the column properties that are
preserved are:

* `DEFAULT`s
* foreign key constraints

but this list will grow as more work is done on #227.

pkg/migrations/op_set_check.go

@@ -27,7 +27,8 @@ func (o *OpSetCheckConstraint) Start(ctx context.Context, conn *sql.DB, stateSch
 	column := table.GetColumn(o.Column)
 
 	// Create a copy of the column on the underlying table.
-	if err := duplicateColumn(ctx, conn, table, *column); err != nil {
+	d := NewColumnDuplicator(conn, table, column)
+	if err := d.Duplicate(ctx); err != nil {
 		return fmt.Errorf("failed to duplicate column: %w", err)
 	}
 
@@ -112,11 +113,9 @@ func (o *OpSetCheckConstraint) Complete(ctx context.Context, conn *sql.DB, s *sc
 	}
 
 	// Rename the new column to the old column name
-	_, err = conn.ExecContext(ctx, fmt.Sprintf("ALTER TABLE IF EXISTS %s RENAME COLUMN %s TO %s",
-		pq.QuoteIdentifier(o.Table),
-		pq.QuoteIdentifier(TemporaryName(o.Column)),
-		pq.QuoteIdentifier(o.Column)))
-	if err != nil {
+	table := s.GetTable(o.Table)
+	column := table.GetColumn(o.Column)
+	if err := RenameDuplicatedColumn(ctx, conn, table, column); err != nil {
 		return err
 	}