text: Title: How do ON DUPLICATE KEY UPDATE?
  Body: Table have a unique constrain on 2 fields.
  When i try to `await MyModel.create(**dict_of_data)` with exist entry in unique fields, i got error:
  `tortoise.exceptions.IntegrityError: (1062, "Duplicate entry...`
  
  Try `await MyModel(**dict_of_data).save(force_update=True)` raise error:
  `tortoise.exceptions.IntegrityError: Can't update object that doesn't exist. PK: None`
  How can i do `ON DUPLICATE KEY UPDATE` for create new or update exist record without many requests and conditional structures?