code: public function readRelatedResource(StoreInterface $store, FetchRelated $request)
      {
          $record = $request->getRecord();
          $result = $this->beforeReadingRelationship($record, $request);
  
          if ($this->isResponse($result)) {
              return $result;
          }
  
          $related = $store->queryRelated(
              $record,
              $request->getRelationshipName(),
              $request->getParameters()
          );
  
          $records = ($related instanceof PageInterface) ? $related->getData() : $related;
          $result = $this->afterReadingRelationship($record, $records, $request);
  
          if ($this->isInvokedResult($result)) {
              return $result;
          }
  
          return $this->reply()->content($related);
      }
docs: Read related resource action.
  
  @param StoreInterface $store
  @param FetchRelated $request
  @return Response