-- Rename a user:

postgres=# alter user dbatest rename to dbaprod;
NOTICE: MD5 password cleared because of role rename
ALTER ROLE
postgres=# \du
List of roles
Role name  | Attributes                                                 | Member of
-----------+------------------------------------------------------------+-----------
dbaprod   |                                                             | {}
postgres  | Superuser, Create role, Create DB, Replication, Bypass RLS  | {}

<< NOTE - AFTER renaming the user, you need to reset the password to same old one.

i.e
-- Change the password a user:

postgres=# alter user dbaprod password 'test';
ALTER ROLE

--- Increase the validity of the user:

postgres=# alter user dbaprod valid until 'Feb 10 2021';
ALTER ROLE