docs: @Delete
      public Maybe<Boolean> invalidateCaches() {
          return Flowable.fromIterable(cacheManager.getCacheNames())
                  .map(cacheManager::getCache)
                  .flatMap(c ->
                          Publishers.fromCompletableFuture(() -> c.async().invalidateAll())
                  ).reduce((aBoolean, aBoolean2) -> aBoolean && aBoolean2);
      }