code: private function buildAuthorizationHeader(array $params)
      {
          foreach ($params as $key => $value) {
              $params[$key] = $key . '="' . rawurlencode($value) . '"';
          }
  
          if ($this->realm) {
              array_unshift(
                  $params,
                  'realm="' . rawurlencode($this->realm) . '"'
              );
          }
  
          return ['Authorization', 'OAuth ' . implode(', ', $params)];
      }
docs: Builds the Authorization header for a request
  
  @param array $params Associative array of authorization parameters.
  
  @return array