chore: allow-list Spanner

[olavloite]

Add the Spanner data client to the allow-list.

Also fixes an error when generating the code for the Type proto of Spanner. This proto has a direct recursive field array_element_type. This is generated as a boxed field, but the to_proto / from_proto methods did not take this into account.

[gemini-code-assist]

Code Review

This pull request correctly adds the Spanner data client to the allow-list. It also introduces a fix for generating code for recursive proto fields in Rust, specifically for types like Spanner's Type proto. A new MapToBoxed flag is added to field annotations to detect when prost will box a field due to recursion, and the to_proto conversion logic in the templates is updated to handle this correctly. The accompanying test updates are thorough and validate the new logic. I have one suggestion to improve the clarity of the mapToBoxed helper function's visited map initialization.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.93%. Comparing base (0a5722d) to head (f92a9b7).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4072   +/-   ##
=======================================
  Coverage   81.93%   81.93%           
=======================================
  Files          78       78           
  Lines        6516     6516           
=======================================
  Hits         5339     5339           
  Misses        832      832           
  Partials      345      345           

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[coryan]

The code LGTM, but it would be nicer if we separated the allow list change from the sidekick changes. Do you mind doing so?

[olavloite]

The code LGTM, but it would be nicer if we separated the allow list change from the sidekick changes. Do you mind doing so?

Sure, I'll split it into two changes.