new: [compose-core] avoid displaying information about optional relations available in quiet mode

bin/compose-core

@@ -2676,10 +2676,12 @@ get_all_relations () {
             ## make recommendation
             echo "$(_display_solves recommended)" | sed -r "s/^/${YELLOW}||${NORMAL} /g" >&2
         fi
+        if [ -z "$QUIET" ]; then
             if [ "${#optional[@]}" != 0 ]; then
                 ## inform about options
                 echo "$(_display_solves optional)"  | sed -r "s/^/${BLUE}||${NORMAL} /g" >&2
             fi
+        fi
         # if [ "${#required[@]}" != 0 ]; then
         #     err "Required relations not satisfied"
         #     return 1