Use composite primary key as part of data Unique record

[sergesku]

Currently, the composite primary key is not part of the data Unique record.
Perhaps it makes sense to add a composite primary key as an additional constructor.

Then

UserAddress
  user  UserId
  address  AddressId

  Primary user address

will generate

data Unique UserAddress = UniquePrimaryUserAddress UserId AddressId

[parsonsmatt]

This was implemented with #1383 and was released with 2.14.

Feel free to reopen if that's not doing what you expected 😄