Fix some OpenAPI issues (#970)

* Fix #933, update externals docs url to current version

* Fix #962, openApi don't err on nonexistent schema

* Fix #954, make OpenAPI rpc output dependent on user privileges

test/fixtures/privileges.sql

@@ -74,3 +74,6 @@ GRANT ALL ON TABLE authors_only TO postgrest_test_author;
 GRANT SELECT (article_id, user_id) ON TABLE limited_article_stars TO postgrest_test_anonymous;
 GRANT INSERT (article_id, user_id) ON TABLE limited_article_stars TO postgrest_test_anonymous;
 GRANT UPDATE (article_id, user_id) ON TABLE limited_article_stars TO postgrest_test_anonymous;
+
+REVOKE EXECUTE ON FUNCTION privileged_hello(text) FROM PUBLIC; -- All functions are available to every role(PUBLIC) by default
+GRANT EXECUTE ON FUNCTION privileged_hello(text) TO postgrest_test_author;

test/fixtures/schema.sql

@@ -1247,6 +1247,9 @@ create function test.test() returns table(test text, value int) as $$
   values ('hello', 1);
 $$ language sql;
 
+create function test.privileged_hello(name text) returns text as $$
+  select 'Privileged hello to ' || $1;
+$$ language sql;
 --
 -- PostgreSQL database dump complete
 --