Updates to keys

[mojaveazure]

This PR updates some infrastructure around keys:

• Class warnings around keys
• Simplify and stabilize logic around handling key warnings
• Fix incorrect documentation
• Add single place to refer to meta data keys

This PR also ups the minimum version of R to 4.1.0 to make use of lambdas

[dcollins15]

Excited to give this a proper read-through in the next day or so! 🔥

Are these changes expected to affect any particular behavior or is this mostly developer-oriented maintenance?

[mojaveazure]

This is predominantly a developer-oriented update. The only user-facing changes are:

• Discontinuing support for R 4.0 (R-release is R 4.3 and expected to become R 4.4. in the spring) due to the use of shorthand function syntax (\() instead of function() {}) for single-statement functions
• Calling Key() on a character now requires explicit quiet = TRUE to suppress warnings. Previously, one could call

Key("mychar", TRUE)

to suppress the warning generated by updating a key, but now one must call

Key("mychar", quiet = TRUE)

to achieve the same effect

[dcollins15]

LGTM! The lambda syntax is slick 😎

Is there any reason users might not want to upgrade to R 4.1.0? I can imagine folks being chuffed at a major upgrade but this seems like a small imposition to me 🤷

[mojaveazure]

The biggest downside in upgrading from R 4.0 to R 4.1 is the need to re-install your package library (R package libraries are specific to the minor version). However, newer cycles of R v4 have introduced several niceities so pushing people to upgrade would be (IMO) a good thing (there's a few features of R 4.2 and 4.3 that I'd like to use, but won't at this point in time to maintain compatibility with R 4.1)