S3 Mode url reconstruction defaults to wrong server type

[mannreis]

We faced an issue when using ncdump to read Zarr from a S3 instance that is not hosted by AWS or Google.

ncdump -h https://bucket.s3.region.example.com/cmip6/CMIP6/CMIP/NASA-GISS/GISS-E2-1-G/historical/r1i1p1f1/day/tasmin/gn/v20181015/#mode=zarr,s3

Noting the "dummy" host on the url of the command above, unfortunately it works. This is because on this NC_s3urlrebuild call, uri->host is overwritten to the default: storage.googleapis.com.

In this PR:

• NCS3SVC is re-declared, so that NCS3UNK != NCS3GS - fixing the issue.
• Optional: Added support to use the host of a url to infer bucket and region inference, similar to AWS.
• Optional: Unit test NC_s3urlrebuild

(edit: links)

[CLAassistant]

All committers have signed the CLA.

[WardF]

Approved pending tests passing.

[WardF]

The failures appear unrelated to the PR, and are part of an issue we're fixing on the Unidata side. This looks good and will be merged shortly.

[WardF]

The certificate issue on our end is resolved so I'm re-running the jobs; hopefully this should all pass, and we'll get this merged! Thanks!

[DennisHeimbigner]

Thanks fo this. We did not support this case because we could find a test site.

[WardF]

The current failure is the result of a combination of two different PRs which both passed checks, but combined, are resulting in a strange error. Once we get that fixed we can re-run the checks and merge this. @DennisHeimbigner this is related to the anonymous dimension issue I reached out about.