Add ORM models for the simulation data

- add new ORM models `ReplaySimulation` and `ReplayedOrder`
  to store the data generated by the routing simulations
- add migrations script to create the corresponding database tables
  + create "replay_simulations" and "replayed_orders" tables
  + add missing check constraints to "orders" table
  + add unique constraint to "orders" table to enable compound key
  + drop unnecessary check constraints from the "orders" table
- add tests for the new ORM models
  + add `simulation`, `replayed_order`, `make_replay_order()`, and
    `pre_order` fixtures
  + add `ReplayedOrderFactor` faker class
- fix some typos

tests/conftest.py

@@ -106,6 +106,7 @@ make_address = fake_data.make_address
 make_courier = fake_data.make_courier
 make_customer = fake_data.make_customer
 make_order = fake_data.make_order
+make_replay_order = fake_data.make_replay_order
 make_restaurant = fake_data.make_restaurant
 
 address = fake_data.address
@@ -114,6 +115,10 @@ city_data = fake_data.city_data
 courier = fake_data.courier
 customer = fake_data.customer
 order = fake_data.order
+pre_order = fake_data.pre_order
+replayed_order = fake_data.replayed_order
 restaurant = fake_data.restaurant
 grid = fake_data.grid
 pixel = fake_data.pixel
+simulation = fake_data.simulation
+simulation_data = fake_data.simulation_data