postgres=# GRANT ALL PRIVILEGES on DATABASE nextcloud_db to nextcloud;
GRANT

postgres=# GRANT CONNECT ON DATABASE nextcloud_db to nextcloud;
GRANT

postgres=# CREATE USER nextcloud;
CREATE ROLE
postgres=# \password nextcloud
Enter new password:
Enter it again:

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     peer
# IPv4 local connections:
host    all             all             127.0.0.1/32            ident
# IPv6 local connections:
host    all             all             ::1/128                 ident
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     all                                     peer
host    replication     all             127.0.0.1/32            ident
host    replication     all             ::1/128                 ident