Alex's R function to grab envvars and R options

A function I’ve written to grab useful values from either envvars or R options, to allow some flexibility in how we access those -- @AlexAxthelm

#' @export
get_database_user <- function(
  envvar = "POSTGRES_USER",
  option = "database_user"
  ) {
  if (Sys.getenv(envvar) != "") {
    return(Sys.getenv(envvar))
  } else if (!is.null(options(option)[[option]])) {
    return(options(option)[[option]])
  } else if (require("rstudioapi") & rstudioapi::isAvailable()) {
    return(rstudioapi::askForPassword("Database User"))
  } else {
    stop("Please add database user as envvar or R option")
  }
}

Start by locating where the R package or scripts define database configuration and where get_database_user would be used. Clarify whether this proposed function should be added and which environment variable, R option, RStudio prompt, and error behavior are required. Done means the agreed behavior is implemented and covered by the repository's existing checks.