Allow specifying the constraint name to disambiguate an embedding (#1430)

Makes previous duck typing regex unnecessary since the FK can be renamed
to a singular name or to any other format.

* Remove embedding with duck typed column names
* Allow embedding by foreign key name
* Add junction disambiguation tests

test/fixtures/data.sql

@@ -526,3 +526,49 @@ INSERT INTO private.pages VALUES (2, 'http://postgrest.org/en/v6.0/admin.html');
 TRUNCATE TABLE private.referrals CASCADE;
 INSERT INTO private.referrals VALUES ('github.com', 1);
 INSERT INTO private.referrals VALUES ('hub.docker.com', 2);
+
+TRUNCATE TABLE big_projects CASCADE;
+INSERT INTO big_projects (big_project_id, name)
+VALUES (1, 'big project 1'),
+       (2, 'big project 2');
+
+TRUNCATE TABLE sites CASCADE;
+INSERT INTO sites (site_id, name, main_project_id)
+VALUES (1, 'site 1', 1),
+       (2, 'site 2', null),
+       (3, 'site 3', 2),
+       (4, 'site 4', null);
+
+TRUNCATE TABLE jobs CASCADE;
+INSERT INTO jobs (job_id, name, site_id, big_project_id)
+VALUES ('bc5d5362-b881-438f-b9f5-7417e08704ed', 'job 1-1', 1, 1),
+       ('3bd52697-033b-4edd-8a28-46a9c04b7c1e', 'job 2-1', 2, 1),
+       ('e6e67e4e-19b1-11e9-ab14-d663bd873d93', 'job 2-2', 2, 2);
+
+TRUNCATE TABLE departments CASCADE;
+TRUNCATE TABLE agents CASCADE;
+INSERT INTO agents (id, name)
+VALUES (1, 'agent 1'),
+       (2, 'agent 2'),
+       (3, 'agent 3'),
+       (4, 'agent 4');
+
+INSERT INTO departments (id, name, head_id)
+VALUES (1, 'dep 1', 1),
+       (2, 'dep 3', 3);
+
+UPDATE agents SET department_id = 1 WHERE id in (1, 2);
+UPDATE agents SET department_id = 2 WHERE id in (3, 4);
+
+TRUNCATE TABLE schedules CASCADE;
+INSERT INTO schedules VALUES(1, 'morning', '06:00:00', '11:59:00');
+INSERT INTO schedules VALUES(2, 'afternoon', '12:00:00', '17:59:00');
+INSERT INTO schedules VALUES(3, 'night', '18:00:00', '23:59:00');
+INSERT INTO schedules VALUES(4, 'early morning', '00:00:00', '05:59:00');
+
+TRUNCATE TABLE activities CASCADE;
+INSERT INTO activities(id, schedule_id, car_id)    VALUES(1, 1, 'CAR-349');
+INSERT INTO activities(id, schedule_id, camera_id) VALUES(2, 3, 'CAM-123');
+
+TRUNCATE TABLE unit_workdays CASCADE;
+INSERT INTO unit_workdays VALUES(1, '2019-12-02', 1, 1, 2, 3);