code: private function getIndexFieldType(ContentType $contentType)
      {
          $newFieldType = new FieldType\TextField();
          $newFieldType->boost = $this->boostFactorProvider->getContentMetaFieldBoostFactor(
              $contentType,
              'text'
          );
  
          return $newFieldType;
      }
docs: Return index field type for the given $contentType.
  
  @param \eZ\Publish\SPI\Persistence\Content\Type $contentType
  
  @return \eZ\Publish\SPI\Search\FieldType