tests: Add test for gcs wif

[Xuanwo]

No description provided.

[saiintbrisson]

https://github.com/Xuanwo/reqsign/blob/9eda80ca9c02ae57afae9fca10c47322d749160f/tests/google/storage.rs#L23-L25
Will require an if of some sort to select either the base64 content or the path, whichever is present.

[Xuanwo]

Will require an if of some sort to select either the base64 content or the path, whichever is present.

reqsign have diffent APIs to handle that from_content vs from_path.