#6083 update examples in File part of Native API: 'Getting File Metadata' section

[pkiraly]

What this PR does / why we need it: It improves the Native API documentation by providing full curl examples for a File regarding call in 'Getting File Metadata' section

Which issue(s) this PR closes: none of them. It is an additional step for solving #6083

Special notes for your reviewer: This PR continue previous pull requests which handles examples regarding dataverses (e.g. #6600). This one is about reformatting a file API call.

Suggestions on how to test this:

cd doc/sphinx-guides
make clean && make html
firefox build/html/api/native-api.html

Check 'Getting File Metadata' section

Does this PR introduce a user interface change?: no

Is there a release notes update needed for this change?: no

Additional documentation: no

[coveralls]

Coverage increased (+0.02%) to 19.471% when pulling 34f6376 on pkiraly:6083-documentation-update-native-API-examples-getting-file-metadata into be6678b on IQSS:develop.

[mheppler]

Everything looks good here, just added an inline comment (line 1785) proposing a simple text change.

[pkiraly]

This PR was developed by Göttingen eResearch Alliance, Germany, and funded by SSHOC, "Social Sciences and Humanities Open Cloud". SSHOC has received funding from the European Union’s Horizon 2020 project call H2020-INFRAEOSC-04-2018, grant agreement #823782.