Reduce privilege requirement in bgw_security

The test `bgw_security` requires escalated privileges to modify
`_timescaledb_config.bgw_job` and set the owner, which does not work
when running tests on an instance without `SUPERUSER` privileges.

Reduce the requirements for the test by switching role before adding
the job, and hence avoid the need to update
`_timescaledb_config.bgw_job` to set the owner.

Commit also clarifies one error message generated on permission errors
for a job.

tsl/src/bgw_policy/job_api.c

@@ -244,7 +244,7 @@ job_delete(PG_FUNCTION_ARGS)
 	if (!has_privs_of_role(GetUserId(), job->fd.owner))
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-				 errmsg("insufficient permissions to delete job for user \"%s\"",
+				 errmsg("insufficient permissions to delete job owned by \"%s\"",
 						GetUserNameFromId(job->fd.owner, false))));
 
 	ts_bgw_job_delete_by_id(job_id);

tsl/test/expected/bgw_security.out

@@ -3,30 +3,41 @@
 -- LICENSE-TIMESCALE for a copy of the license.
 \set ROLE_ADMIN :TEST_DBNAME _admin
 \c :TEST_DBNAME :ROLE_SUPERUSER
-CREATE ROLE :ROLE_ADMIN;
+CREATE ROLE :ROLE_ADMIN LOGIN;
 GRANT :ROLE_ADMIN TO :ROLE_DEFAULT_PERM_USER;
 \c :TEST_DBNAME :ROLE_SUPERUSER
 CREATE TABLE custom_log (ts integer, msg text);
 GRANT ALL ON custom_log TO PUBLIC;
 CREATE PROCEDURE custom_job(integer, jsonb) AS $$
   INSERT INTO custom_log values($1, 'custom_job');
 $$ LANGUAGE SQL;
+SET ROLE :ROLE_ADMIN;
 SELECT add_job('custom_job', '1h') AS job_id \gset
--- Set the owner of the job to the admin role
-UPDATE _timescaledb_config.bgw_job SET owner = :'ROLE_ADMIN' WHERE id = :job_id;
+RESET ROLE;
 SELECT id, proc_name, owner FROM _timescaledb_config.bgw_job WHERE id = :job_id;
   id  | proc_name  |         owner         
 ------+------------+-----------------------
  1000 | custom_job | db_bgw_security_admin
 (1 row)
 
 \c :TEST_DBNAME :ROLE_DEFAULT_PERM_USER_2
--- We should fail to execute the job since we do not own it or belong
--- to the group that owns it.
+-- We should fail to execute and delete the job since we do not own it
+-- or belong to the group that owns it.
 \set ON_ERROR_STOP 0
 CALL run_job(:job_id);
 ERROR:  insufficient permissions to run job 1000
+SELECT delete_job(:job_id);
+ERROR:  insufficient permissions to delete job owned by "db_bgw_security_admin"
 \set ON_ERROR_STOP 1
 \c :TEST_DBNAME :ROLE_DEFAULT_PERM_USER
 -- This should succeed since the role belongs to the job owner group.
 CALL run_job(:job_id);
+-- This should succeed since we belong to the owners role.
+SELECT delete_job(:job_id);
+ delete_job 
+------------
+
+(1 row)
+
+\c :TEST_DBNAME :ROLE_SUPERUSER
+DROP ROLE :ROLE_ADMIN;

tsl/test/sql/bgw_security.sql

@@ -5,7 +5,7 @@
 \set ROLE_ADMIN :TEST_DBNAME _admin
 \c :TEST_DBNAME :ROLE_SUPERUSER
 
-CREATE ROLE :ROLE_ADMIN;
+CREATE ROLE :ROLE_ADMIN LOGIN;
 GRANT :ROLE_ADMIN TO :ROLE_DEFAULT_PERM_USER;
 
 \c :TEST_DBNAME :ROLE_SUPERUSER
@@ -17,22 +17,29 @@ CREATE PROCEDURE custom_job(integer, jsonb) AS $$
   INSERT INTO custom_log values($1, 'custom_job');
 $$ LANGUAGE SQL;
 
+SET ROLE :ROLE_ADMIN;
 SELECT add_job('custom_job', '1h') AS job_id \gset
 
--- Set the owner of the job to the admin role
-UPDATE _timescaledb_config.bgw_job SET owner = :'ROLE_ADMIN' WHERE id = :job_id;
+RESET ROLE;
 
 SELECT id, proc_name, owner FROM _timescaledb_config.bgw_job WHERE id = :job_id;
 
 \c :TEST_DBNAME :ROLE_DEFAULT_PERM_USER_2
 
--- We should fail to execute the job since we do not own it or belong
--- to the group that owns it.
+-- We should fail to execute and delete the job since we do not own it
+-- or belong to the group that owns it.
 \set ON_ERROR_STOP 0
 CALL run_job(:job_id);
+SELECT delete_job(:job_id);
 \set ON_ERROR_STOP 1
 
 \c :TEST_DBNAME :ROLE_DEFAULT_PERM_USER
 
 -- This should succeed since the role belongs to the job owner group.
 CALL run_job(:job_id);
+
+-- This should succeed since we belong to the owners role.
+SELECT delete_job(:job_id);
+
+\c :TEST_DBNAME :ROLE_SUPERUSER
+DROP ROLE :ROLE_ADMIN;