Specially process or disallow tbl_ts input to new_epi_df

[brookslogan]

devtools::load_all("/home/fullname/files/tooling/epiprocess/", export_all=FALSE)
#> ℹ Loading epiprocess
original_edf = new_epi_df(tibble::tibble(geo_value=1, time_value=1, age_value=1, value=1),
                          additional_metadata=list(other_keys="age_value"))
corresponding_tsibble = tsibble::as_tsibble(original_edf)
tsibble::key(corresponding_tsibble)
#> [[1]]
#> geo_value
#> 
#> [[2]]
#> age_value
recovered_edf = as_epi_df(corresponding_tsibble)
attr(recovered_edf, "metadata")$other_keys
#> [1] "age_value"
not_recovered_edf = new_epi_df(corresponding_tsibble)
attr(not_recovered_edf, "metadata")$other_keys
#> NULL

^{Created on 2022-08-25 by the reprex package (v2.0.1)}

I think we'd prefer one of the following:

• Raise an error if x is a tbl_ts.
• Raise an error if x is a tbl_ts that has a tsibble::key including anything other than geo_value.
• Make new_epi_df behave the same way as as_epi_df when given a tbl_ts.