[unconfirmed] R should be able to write to a config file taking a data file path as an argument

[soniamitchell]

• The config.yaml file should be written to tempfile(fileext = ".yaml)
• data_products can be added using add_read() and add_write(); note that these function names are already taken by functions used to generate user-written config files for the unit tests
• The location of this file could be passed in the handle

If the CLI is wrapped, then check first whether fair is installed:

if (Sys.which("fair") == "")
  stop("fair CLI isn't installed")

• If it's not, do we want to install it automatically (as is done in the CI) or throw an error and prompt the user to install it themselves?
• Likewise for the registry.
• Do we want the user to create their own virtual environment, or create and activate one automatically (as is done in the CI)?