static DependencyInjector ofSingletons(Iterable<Object> singletons) {
        return new DefaultDependencyInjector(singletons);
    }
Returns a {@link DependencyInjector} that injects dependencies using the specified singleton instances.
The instances are {@linkplain AutoCloseable#close() closed} if it implements {@link AutoCloseable}
when the {@link Server} stops.
core/src/main/java/com/linecorp/armeria/common/DependencyInjector.java