postgis: make give_me_a_connection public

[pjonsson]

Reason for this pull request

This makes OWS ping work with
the postgis index driver.

Proposed changes

• Closes #xxxx

• Tests added / passed

• Fully documented, including docs/about/whats_new.rst for all changes

---

📚 Documentation preview 📚: https://datacube-core--1782.org.readthedocs.build/en/1782/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.69%. Comparing base (d5fa879) to head (20bcb5b).
Report is 458 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1782   +/-   ##
========================================
  Coverage    85.69%   85.69%           
========================================
  Files          149      149           
  Lines        16137    16137           
========================================
  Hits         13828    13828           
  Misses        2309     2309           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[SpacemanPaul]

This is a horribly named function and I'd rather not make it public :)

Surely there's a better way to get OWS ping working.

[pjonsson]

I completely agree about naming and preferring that the thing remains hidden. I don't know how the API design normally goes, but it does seem reasonable to provide users with a way to get a database connection if they really want one. In the best of worlds they have a high-level API that corresponds to their needs and they won't need a raw connection, but reality tends to get in the way of those kind of things.

And I don't see how to fix things on the OWS side without resorting to isinstance checks, and they are also quite bad.

[SpacemanPaul]

If you need a raw db connection, then you need to be intimately familiar with driver-specific details of the database schema.

OWS already has a framework for driver-specific behaviour.