fix: login with uppercase and mixed case role names

PostgREST failed when querying role settings where current
role name contained uppercase letters. This commit resolves
it by quoting the CURRENT_USER.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

test/io/fixtures/replica.sql

@@ -13,7 +13,7 @@ create table replica.items as select x as id from generate_series(1, 10) x;
 DROP ROLE IF EXISTS postgrest_test_anonymous;
 CREATE ROLE postgrest_test_anonymous;
 
-GRANT postgrest_test_anonymous TO :PGUSER;
+GRANT postgrest_test_anonymous TO :"PGUSER";
 
 GRANT USAGE ON SCHEMA replica TO postgrest_test_anonymous;