function isRemoteRef(obj, key) {
  return key === '$ref' &&
  typeof obj[key] === 'string' &&
  obj[key] !== undefined &&
  !obj[key].startsWith(localPointer) &&
  stringIsAValidUrl(obj[key]);
}
Determines if a value of a given key property of an object
is a remote reference with key $ref and value that is a valid url
@param {object} obj - parent object of the $ref property
@param {string} key - property key to check
@returns {boolean} - true if the property key is $ref and the value is a valid url
otherwise false