Use SDK Updater for automated spec updates

[AndreyVMarkelov]

Summary

• replace the missing SPEC_UPDATE_TOKEN with the SDK Updater GitHub App token flow
• authenticate to AWS through repository-scoped OIDC and load the App credentials from Secrets Manager
• close superseded spec_update_* pull requests and label new automated updates
• update checkout to v7

Why

The Spec Update workflow successfully generated and validated the latest API spec, but failed to create its pull request because SPEC_UPDATE_TOKEN was not configured. This applies the authentication and PR-management pattern introduced by dropbox/dropbox-sdk-go-unofficial@924ad8f.

Validation

• actionlint passes after ignoring its stale metadata warning for the proven actions/create-github-app-token@v3 client-id input
• git diff --check

Test plan

• Confirm the repository-scoped AWS OIDC role exists and can read sdk-updater-github-app
• Confirm the SDK Updater GitHub App is installed for this repository
• Run the workflow manually on this branch and verify AWS authentication and App token generation
• After merge and the next spec change, verify an automated-spec-update PR is opened and CI runs

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 10.68%. Comparing base (4f9a16d) to head (5d74c81).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #335   +/-   ##
=======================================
  Coverage   10.68%   10.68%           
=======================================
  Files           6        6           
  Lines        5775     5775           
  Branches        4        4           
=======================================
  Hits          617      617           
  Misses       5158     5158           

Flag	Coverage Δ
unit	10.68% <ø> (ø)

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