refactor: Make JWT authorization a middleware

This follows the style of wai-middleware-auth package and
makes the JWT parsing a middleware.

Co-authored-by: Wolfgang Walther <walther@technowledgy.de>

test/io/fixtures.sql

@@ -73,9 +73,3 @@ create function reload_pgrst_config() returns void as $_$
 begin
   perform pg_notify('pgrst', 'reload config');
 end $_$ language plpgsql ;
-
-create or replace function raise_bad_pt() returns void as $$
-begin
-  raise sqlstate 'PT40A' using message = 'Wrong';
-end;
-$$ language plpgsql;