Fixes for metadata credential fetching

[contradict]

The first change is for a change in the Julia HTTP library, data is now body.

The second is for a change it the Google API, the format of the Content-Type header has changed.

With these two changes, MetadataCredentials works on GCE instances.

[mattBrzezinski]

This package doesn't look like it gets too much attention sadly. When I have some spare time I can look into the CI error and fix it.

Would you mind possibly adding some tests to this? Although looking at what exists currently there doesn't seem to be much there.

[JockLawrie]

Hi Matt, I am no longer using GCP and therefore am no longer maintaining this package. If you'd like to fork this repo I'll link to the fork from here and archive this repo.

[mattBrzezinski]

Hi Matt, I am no longer using GCP and therefore am no longer maintaining this package. If you'd like to fork this repo I'll link to the fork from here and archive this repo.

I think it can continue to live in the JuliaCloud org, it seems like an appropriate place.

[Alexander-Barth]

I can confirm that this PR is still necessary for MetadataCredentials().
Would it be possible of somebody from the JuliaCloud org would merge this PR?

Thanks for this great package (and PR :-)) !