You can rename a column using the following statement:
ALTER TABLE table_name RENAME COLUMN column_name TO new_column_name;
However, this brings the old column out of commission immediately. Any use sites that used the old column name will start having problems.
Is there a way to put the table into a transitory state in which both the old and new name can be used to refer to the column, so that I can move over my clients and then afterwards decommission the old name?