private static <T> Iterable<T> concatAndDedup(Iterable<T> first, Iterable<T> second) {
        return Stream.concat(Streams.stream(first), Streams.stream(second)).distinct()
                     .collect(toImmutableList());
    }
Adds examples to the {@link ServiceSpecification} and {@link ServiceInfo} objects.
@param spec Spec itself.
@return new {@link ServiceSpecification} with examples.
core/src/main/java/com/linecorp/armeria/server/docs/ExampleSupport.java