Add base_name var and use it

[AlCutter]

This PR introduces a base_name variable to the witness terraform module, and uses it when naming resources it creates.

This allows for deploying multiple independent instances within the same project.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 22.63%. Comparing base (3c58af4) to head (40c9e51).
⚠️ Report is 295 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #495       +/-   ##
===========================================
- Coverage   51.05%   22.63%   -28.42%     
===========================================
  Files          11       28       +17     
  Lines         903     1975     +1072     
===========================================
- Hits          461      447       -14     
- Misses        374     1451     +1077     
- Partials       68       77        +9     

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[mhutchinson]

Can you explain why? I don't see anything breaking here, but it makes a few minor ergonomic regressions. The base name seems to get used directly for naming different resources, without any suffix. I don't think this causes a problem because each resource type is a different namespace, but it was nice that the service was foo-service rather than just foo. And the display name was intentional before, and now it's just the resource ID.

[AlCutter]

Can you explain why? I don't see anything breaking here, but it makes a few minor ergonomic regressions. The base name seems to get used directly for naming different resources, without any suffix. I don't think this causes a problem because each resource type is a different namespace, but it was nice that the service was foo-service rather than just foo. And the display name was intentional before, and now it's just the resource ID.

The driver is to enable multiple instances to be deployed in the same project.

Spanner display name I'd have happily removed and left unset, but it's only there because it's a required field.

Dropping -service was intentional as it felt somewhat redundant having thing.myname-thing, but I can add that style back in if you feel strongly that it's better.

[mhutchinson]

Sure, as long as it's intentional. I guessed this was the intent, but raised a yellow flag because base_name implied it was to be built on. Go ahead!

[AlCutter]

Sure, as long as it's intentional. I guessed this was the intent, but raised a yellow flag because base_name implied it was to be built on. Go ahead!

Good call, thanks for checking!