Prevent submission of DOIs with non-standard whitespace

[njahn82]

httr::GET("https://api.unpaywall.org/v2/10.1177/ 0042098012452322&email=najko.jahn@gmail.com", 
    httr::timeout(5))
#> Error in curl::curl_fetch_memory(url, handle = handle): Timeout was reached: [api.unpaywall.org] Operation timed out after 5003 milliseconds with 0 bytes received

^{Created on 2021-09-09 by the reprex package (v2.0.0)}

[njahn82]

https://stackoverflow.com/questions/56782045/how-to-trim-white-spaces-when-trimws-is-not-working