Use apiTokenServiceName constant and not the string

Change-Id: If695b2476752c3beccfe0d11656d96ed1f3f7fde
diff --git a/R/KorAPConnection.R b/R/KorAPConnection.R
index 53fbc1c..cdc51f8 100644
--- a/R/KorAPConnection.R
+++ b/R/KorAPConnection.R
@@ -114,14 +114,14 @@
 #' }
 #'
 setMethod("clearApiToken", "KorAPConnection",  function(kco) {
-  key_delete("RKorAPClientAPIToken", kco@KorAPUrl)
+  key_delete(apiTokenServiceName, kco@KorAPUrl)
 })
 
 #' @import keyring
 getApiToken <- function(KorAPUrl) {
   if ("keyring" %in% installed.packages()[,1 ]&& has_keyring_support()
-         && KorAPUrl %in% key_list(service = "RKorAPClientAPIToken"))
-         key_get("RKorAPClientAPIToken", KorAPUrl)
+         && KorAPUrl %in% key_list(service = apiTokenServiceName))
+         key_get(apiTokenServiceName, KorAPUrl)
   else
     NULL
 }