Fix a typo, follow our acceptance test naming guidelines, simplify some logic, and handle an unhandled error.
Implement content_md5, content_type, extension_headers support.
- re-add ‘testAccPreCheck()’ to acceptance tests, to ensure necessary GOOGLE_* env vars are set for Acceptance tests. - remove unused code from datasource - use URL signature (base64 encoded) as data source ID instead of full URL