docs: explain origin of identifiers in aggregate()

[conradoplg]

Closes #697

[github-actions]

Visit the preview URL for this PR (updated for commit e536be3):

https://frost-book--pr956-aggregate-docs-ky6kwijm.web.app

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.46%. Comparing base (1882937) to head (e536be3).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #956   +/-   ##
=======================================
  Coverage   77.46%   77.46%           
=======================================
  Files          41       41           
  Lines        4300     4300           
=======================================
  Hits         3331     3331           
  Misses        969      969           

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[mergify]

Merge Queue Status

✅ The pull request has been merged at e536be3

This pull request spent 16 seconds in the queue, including 2 seconds running CI.
The checks were run on draft #972.

Required conditions to merge

• #approved-reviews-by >= 1 [🛡 GitHub branch protection]
  • core: fix unused warning due to compiler bug #971
  • docs: explain origin of identifiers in aggregate() #956
• #changes-requested-reviews-by = 0 [🛡 GitHub branch protection]
  • core: fix unused warning due to compiler bug #971
  • docs: explain origin of identifiers in aggregate() #956
• #review-threads-unresolved = 0 [🛡 GitHub branch protection]
  • core: fix unused warning due to compiler bug #971
  • docs: explain origin of identifiers in aggregate() #956
• base=main