improve type safety with rlang or assertthat or checkmate

[e-kotov]

Improve type safety of the package

• either use assertthat https://github.com/hadley/assertthat
• or rlang (details here https://josiahparry.com/posts/2024-06-30-type-safety/)

[Robinlovelace]

{checkmate} is another option, mild preference for {rlang} as it's already an import. Simple is good.

[e-kotov]

The {rlang} option is problematic, it is more of a hack right now and will (may) be superseded by a separate package: tidyverse/design#160 .

Therefore, I will either use {checkmate}, as it is still actively maintained, or will simply do with our internal check functions, as we have a lot of argument normalisation functions anyway.

[Robinlovelace]

Sounds good, simple good, and it is possible to over-engineer (and over-think) such things, stopifnot() also an option..