new: [rsync-backup-target] improve error messages !minor

rsync-backup-target/hooks/init

@@ -16,12 +16,13 @@ set -e
 service_def=$(get_compose_service_def "$SERVICE_NAME")
 
 admin_keys=$(echo "$service_def" | shyaml -y get-value options.admin 2>/dev/null) || {
-    err "You must specify a ${WHITE}admin${NORMAL} struct to use this service"
+    err "You must specify a ${WHITE}admin${NORMAL} struct in ${DARKYELLOW}$SERVICE_NAME${NORMAL}'s options"
     exit 1
 }
 
 [ "$(echo "$admin_keys" | shyaml -y get-type 2>/dev/null)" == "struct" ] || {
-    err "Invalid value type for ${WHITE}admin${NORMAL}, please provide a struct"
+    err "Invalid value type for ${WHITE}admin${NORMAL} in" \
+        "${DARKYELLOW}$SERVICE_NAME${NORMAL}'s options, please provide a struct"
     exit 1
 }