Postgresql: Permission denied to schema to user created based on master with rights

I'm trying to write a function that eventually will rotate users. Currently I have the code below which works and creates a new user using the prior user which ultimately has the same rights as the master user, ie, can do everything.

select mysch.dblink('dbname=mydb user=themasteruser password=abc123 connect_timeout=200000 host=localhost', 'CREATE USER newuname WITH PASSWORD ''pass1'' CREATEDB CREATEROLE;GRANT rds_superuser TO newuname;');


DROP SERVER IF EXISTS fs_link_b CASCADE;
CREATE SERVER fs_link_b FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host 'localhost', port '5432', dbname 'mydb ', connect_timeout '200000');
CREATE USER MAPPING FOR newuname SERVER fs_link_b OPTIONS ("user" 'newuname',password 'pass1');
ALTER SERVER fs_link_b OWNER TO newuname;

However, when I make a connection with the above created user and I try to run the query below:

select * from mysch.dblink('link_b', 'select usename from PG_USER limit 1;') as t(uu text);

I get this error:

SQL Error [42501]: ERROR: permission denied for schema mysch

If I created the user based on a master user, then should it not have all rights as the master user as created above? Or Do I need to do a bunch of individual GRANTS still?