Replace udunits2 with units

[nanu1605]

Replace udunits2 with units package as udunits2 is an orphaned package.

[Aariq]

Looks like you need to run scripts/generate_dependencies.R

[nanu1605]

@Aariq, all the CI checks are passing so I think the replacement worked

[infotroph]

Woohoo! This is looking great.

[nanu1605]

@infotroph, The changes you suggested are done. Please review it once

[Aariq]

Maybe some simple tests for the new functions would be a good idea? A couple correctness tests and maybe a test that the output is indeed numeric (and not class "units")

[infotroph]

@nanu1605 This looks good, thank you. I support @Aariq's suggestion -- would you be willing to take a stab at some tests? I can help convert them into testthat format if you get stuck, but start by writing down the function calls you'd use for the correctness tests and how you'd decide the output is correct.

[nanu1605]

@infotroph @Aariq Sure I will try writing the tests for ud_convert

[mdietze]

@infotroph does this PR pass your requested changes?

[dlebauer]

Please update changelog

[nanu1605]

@dlebauer should i update CHANGELOG.md for this PR before merging?

[nanu1605]

Sorry I closed it by mistake

Changelog updated