Override imapfilter's certificate storage

src/imapdomo.skel

         echo -n "  -v"
     fi
     echo -n "  -c $IMAPDOMO_HOME/main.lua"
+    if test -n "$Certs"
+    then
+        echo -n " -t $Certs"
+    fi
 }
 
 show_version() {
     local LogDir    # directory to store logs
     local HeaderDir # directory to store headers by save_header()
     local CdTo      # change dir to this before running imapfilter
+    local Certs     # certificate storage
     CfgDir="$IMAPDOMO_CFGDIR"
     LogDir="$IMAPDOMO_USER_CACHE/logs"
     HeaderDir="$IMAPDOMO_USER_CACHE/headers"
+    Certs="$IMAPDOMO_CFGDIR/certificates"
     Debug=false
     #shellcheck disable=SC2034
     while true; do case $1 in
-        -c) CdTo="$2"; shift 2 || usage -w "missing value to: $1" ;;
+        -c) CdTo="$2";  shift 2 || usage -w "missing value to: $1" ;;
         -d) Debug=true; PRETTY_DEBUG=true; shift ;;
+        -t) Certs="$2"; shift 2 || usage -w "missing value to: $1" ;;
         -l) lshandlers; exit ;;
         -V|--version-semver) show_semversion ;;
         --version) show_version ;;