Fix issue tools::toTitleCase() does not accept factos as input

[wangchen46]

Replace tools::toTitleCase() to function propercase.

[fukuhiro2023]

Thank you for your update. I believe the functionality of propercase() in forestly is slightly differenet from that of tools::toTitleCase().

tools::toTitleCase("american indian or alaska native") 
# > "American Indian or Alaska Native"

forestly:::propercase("american indian or alaska native")
# > "American indian or alaska native"

It may be better to keep tools::toTitleCase(), but add as.character() before it to ensure successful conversion when the input is a factor.

[wangchen46]

@fukuhiro2023, Thank you! I revert to use tools::toTitleCase(). I have added check for SEX if input is factor or not. If factor, will convert to character vector before putting into tools::toTitleCase(). For other inputs (i.e RACE, EPOCH), type of these inputs has converted to be character vector when applying tolower::() as tested, and thus I did not add check for these inputs but only SEX. Let me know your thoughts.

[elong0527]

I would suggest to write a helper function for pre-processing of the input data.

The current implementation will break the order defined in factor that will introduce unexpected behavior from user perspective. Specifically:

• based on input, identify all variables required.
• if a variable is a char using tools::toTitleCase()
• if a variable is a factor change the levels using tools::toTitleCase()

x <- factor(c("there is one", "that is two", "here is three"))
levels(x) <- tools::toTitleCase(levels(x))
x

[elong0527]

I just updated propercase and titlecase to handle both factor and char with AI.

unit test are added.

Feel this is sufficient for this PR to close #92.

However, we should consider if we really need format_ae_listing. Maybe a wrapper of prepare_ae_listing would be sufficient as its intention is to generate a AE listing.

https://merck.github.io/metalite.ae/reference/prepare_ae_listing.html