Summary:
- Use `FocusInfo` type instead of a raw string (I'll add another field to it in the next diff and it made sense to keep the changes separate).
- `userSelectedGenerationId` now has the type of `string | undefined` for consistency.
Reviewed By: fabiomassimo
Differential Revision: D23160820
fbshipit-source-id: f210d93b9ed7cb25eb3c2c8e6e6aadec4dc872d7
4fc63da386