public function addRelationship($key, $relation, array $links=[], array $meta=[], array $options=[]) {
		$this->ensureResourceObject();
		
		$options = array_merge(self::$defaults, $options);
		
		$relationshipObject = $this->resource->addRelationship($key, $relation, $links, $meta);
		
		if ($options['includeContainedResources']) {
			$this->addIncludedResourceObject(...$relationshipObject->getNestedContainedResourceObjects());
		}
	}