new: [rsync-backup-target] prevent duplicate key for different identifier

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

rsync-backup-target/hooks/init

@@ -29,9 +29,14 @@ local_path_key=/etc/rsync/keys
 host_path_key="$SERVICE_CONFIGSTORE${local_path_key}"
 key_nb=0
 
-volume_keys=()
-all_keys=" "
+## ident are unique by construction (they are struct keys)
+## but keys need to be also unique
+declare -A keys
 while read-0 ident key; do
+    if [ "${keys[$key]}" ]; then
+        err "Duplicate key: key for ident '$ident' is same as ident '${keys["$key"]}'."
+        exit 1
+    fi
     if ! [[ "$ident" =~ ^[a-zA-Z0-9._-]+$ ]]; then
         err "Invalid identifier '$ident'," \
             "please use only alphanumerical char, dots, dash or underscores."
@@ -39,10 +44,9 @@ while read-0 ident key; do
     fi
     debug "Creating access key for ${ident}" || true
     echo "$key" | file_put "$host_path_key/${ident}.pub"
+    keys["$key"]="$ident"
 done < <(echo "$keys" | shyaml key-values-0)
 
-volume_keys+=("$host_path_key:$local_path_key:ro")
-
 init-config-add "\
 $SERVICE_NAME:
   volumes: