Keeping objects within latent_individual class

[athowes]

In #52 I've found that after making some alterations to an object of class latent_individual that I need to recall as_latent_individual in order for epidist::epidist to work:

obs_prep_reduced <- obs_prep |>
  dplyr::group_by(district) |>
  dplyr::mutate(n = dplyr::n()) |>
  dplyr::filter(n > 30) |>
  dplyr::select(-n) |>
  dplyr::ungroup()

obs_prep_reduced <- as_latent_individual(obs_prep_reduced)

This doesn't seem to be ideal. Probably something easy to fix here.

[seabbs]

Have a look at the class system in scoringutils as I think this has been resolved there by @Bisaloo

[athowes]

Maybe can be fixed by #329.

[athowes]

Closing as duplicate of #399.