GET /seats
Get the list of available seats.
POST /purchase {"row": 3, "column": 4}
Purchase a ticket for the specified seat;
On success returns a string token of the sold ticket.
POST /return {"token": "9b674be1-b42e-4659-b54f-0663e5d4b218"}
Return a ticket with provided token.
POST /stats?password=super_secret
Display statistics on sold tickets.