Do not run tests or build vignettes in CRAN

Since I cannot set credentials in CRAN, I need to disable running tests or building vignettes in CRAN.

Read this for more info: https://cran.r-project.org/web/packages/googlesheets/vignettes/managing-auth-tokens.html#the-making-of-googlesheets.tar.gz-for-cran

tests/testthat.R

@@ -1,4 +1,6 @@
 library(testthat)
 library(DataSpaceR)
 
-test_check("DataSpaceR")
+if (identical(tolower(Sys.getenv("NOT_CRAN")), "true")) {
+  test_check("DataSpaceR")
+}

vignettes/Intro_to_DataSpaceR.Rmd

@@ -9,6 +9,17 @@ vignette: >
   %\VignetteEncoding{UTF-8}
 ---
 
+```{r, echo = FALSE, warning=FALSE, message=FALSE}
+NOT_CRAN <- identical(tolower(Sys.getenv("NOT_CRAN")), "true")
+knitr::opts_chunk$set(
+  collapse = TRUE,
+  comment = "#>",
+  purl = NOT_CRAN,
+  eval = NOT_CRAN
+)
+```
+
+
 This package provides a thin wrapper around [Rlabkey](https://cran.r-project.org/web/packages/Rlabkey/index.html) and connects to the the [CAVD DataSpace](https://dataspace.cavd.org) database, making it easier to fetch datasets from specific studies.