[FR] create module fct/utils without a trailing underscore: mod_FixHumanity_fct_.R

[kwbyron-lilly]

Is your feature request related to a problem? Please describe.
Most modules do not require multiple fct or utils, so often I am not adding additional descriptors to the file name:
add_module("FixHumanity", fct = "")
but this generates a file with a trailing underscore: mod_FixHumanity_fct_.R

I would like to be able to just create the file: mod_FixHumanity_fct.R

Describe the solution you'd like
test for empty string passed to fct or util and drop trailing underscore.

Describe alternatives you've considered
I tried passing TRUE to the variables, but the name validation returns them as a string, bypassing isTRUE() in ifelse statements. Using NA would be unintuitive.

Additional context
how the elements are pasted is generating the extra underscore:
https://github.com/ThinkR-open/golem/blob/ba7f50030369ac62967fe6c38204a469de051dc0/R/add_r_files.R#L104C2-L112C2