CRAN policy: authentication

[jburkhardt]

You write information messages to the console that cannot be easily
suppressed.
Instead of print()/cat() rather use message()/warning() or
if(verbose)cat(..) if you really have to write text to the console.
(except for print() and summary() functions

Please ensure that your functions do not write by default or in your
examples/vignettes/tests in the user's home filespace (including the
package directory and getwd()). That is not allowed by CRAN policies.
Please only write/save files if the user has specified a directory in
the function themselves. Therefore please omit any default path =
getwd() in writing functions.
In your examples/vignettes/tests you can write to tempdir().
f.i.: authenticate()

You can unwrap the example of authenticate if there is no need for a
token for the function. If it takes longer than 5s, wrap it in \donttest.

When creating the examples please keep in mind that the structure
would be desirable:
\examples{
examples for users and checks:
executable in < 5 sec
\dontshow{
examples for checks:
executable in < 5 sec together with the examples above
not shown to users
}
\donttest{
further examples for users; not used for checks
(f.i. data loading examples, or time consuming functions )
}
\dontrun{
not used by checks, not used by example()
adds the comment ("# Not run:") as a warning for the user.
cannot run (e.g. because of missing additional software,
missing API keys, ...)
}
if(interactive()){
functions not intended for use in scripts,
or are supposed to only run interactively
(f.i. shiny)
}
}

[jburkhardt]

use input list instead of readline()
list containing: - client_id
- client_secret
- developer_token