[Feature]: Add primary keys for database tables #36

db=# \d apalis.jobs
                               Table "apalis.jobs"
    Column    |           Type           | Collation | Nullable |     Default
--------------+--------------------------+-----------+----------+-----------------
 job          | bytea                    |           | not null |
 id           | text                     |           | not null |
 job_type     | text                     |           | not null |
 status       | text                     |           | not null | 'Pending'::text
 attempts     | integer                  |           | not null | 0
 max_attempts | integer                  |           | not null | 25
 run_at       | timestamp with time zone |           | not null | now()
 last_result  | jsonb                    |           |          |
 lock_at      | timestamp with time zone |           |          |
 lock_by      | text                     |           |          |
 done_at      | timestamp with time zone |           |          |
 priority     | integer                  |           |          | 0
 metadata     | jsonb                    |           |          |
Indexes:
    "jtidx" btree (job_type)
    "lidx" btree (lock_by)
    "sidx" btree (status)
    "tidx" btree (id)
    "unique_job_id" UNIQUE, btree (id)
Foreign-key constraints:
    "fk_worker_lock_by" FOREIGN KEY (lock_by) REFERENCES apalis.workers(id)
Triggers:
    notify_workers AFTER INSERT ON apalis.jobs FOR EACH ROW EXECUTE FUNCTION apalis.notify_new_jobs()

db=# \d apalis.workers
                          Table "apalis.workers"
    Column    |           Type           | Collation | Nullable | Default
--------------+--------------------------+-----------+----------+----------
 id           | text                     |           | not null |
 worker_type  | text                     |           | not null |
 storage_name | text                     |           | not null |
 layers       | text                     |           | not null | ''::text
 last_seen    | timestamp with time zone |           | not null | now()
 started_at   | timestamp with time zone |           |          |
Indexes:
    "idx" btree (id)
    "lsidx" btree (last_seen)
    "unique_worker_id" UNIQUE, btree (id)
    "wtidx" btree (worker_type)
Referenced by:
    TABLE "apalis.jobs" CONSTRAINT "fk_worker_lock_by" FOREIGN KEY (lock_by) REFERENCES apalis.workers(id)