Convert username and supervisor to lower case.

create_new_user.sh

 #!/bin/bash
 SCRIPTPATH="$( cd -- "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
 
+
 set -o nounset
 set -o errexit
 
@@ -12,6 +13,7 @@ fi
 
 # Variables
 NEW_USER=${1}
+NEW_USER="${NEW_USER,,}"
 ADMINPASSWORD=''
 binddn=${SUDO_USER}@wurnet.nl
 declare -A DN_ARRAY
@@ -125,6 +127,7 @@ fi
 if [ "$STUDENT" == "Y" ]
 then 
     read -p "Who is the supervisor of $NEW_USER ? " SUPERVISOR
+    SUPERVISOR="${SUPERVISOR,,}"
     read -p "What is the end date for access for $NEW_USER ? [${DEFAULT_END_DATE}] " END_DATE
     END_DATE=${END_DATE:-${DEFAULT_END_DATE}}
     echo