More token clean up

[hadley]

• Deprecate set_renv in favour of cache
• Default cache to FALSE
• Export token_cache_path()
• Import deprecated to match recommended style

Fixes #438

[llrs]

• Deprecate set_renv in favour of cache: OK
• Default cache to FALSE: Why? This would be another breaking change for users.
• Export token_cache_path(): OK
• Import deprecated to match recommended style: Which style do you refer to? There isn't any style set for this package.
• Not sure I understand how these changes fix rtweet authentication not working for script running as a local job #438. Wouldn't the token generated with create_token would already be cached and used as default for subsequent calls (without this PR)?

[hadley]

I think having create_token() overwrite a file on disk by default is extremely surprising; creating a token in one app, should not (by default) affect every other app. Yes, I think overhauling auth is going to break existing code, but in conjunction with #469, I think it's very much worth it.

Standard deprecation style is documented at https://lifecycle.r-lib.org/articles/communicate.html#deprecating-an-argument-providing-a-new-default-1

Hmmm, yes, maybe this doesn't fix 438, except to reduce confusion over exactly what is happening when you create a token.

For question that directly related to code, do you mind asking them comments in the PR? That makes it easier to follow the individual threads of discussion.

[hadley]

Also might be better to just close this and #530, and attack in a single PR that addresses #469.

[hadley]

Closing since I'm now pretty sure this isn't going to be useful once we've fully considered auth.