Attest docker images

[alvarof2]

Adds a GitHub attestation job to the docker builds WFs (push and release), so that GitHub attestation is added to images (public Fulcio, as this is a public repo).

This attestation can then be validated by Policy Controller so that only attested images are accepted in the GKE clusters.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 43aee00aa3

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.2%. Comparing base (5f17d27) to head (50e9f26).

Additional details and impacted files

@@              Coverage Diff               @@
##           celo-rebase-17    #442   +/-   ##
==============================================
  Coverage            76.2%   76.2%           
==============================================
  Files                 591     591           
  Lines               74215   74215           
==============================================
+ Hits                56585   56586    +1     
+ Misses              17486   17485    -1     
  Partials              144     144           

Flag	Coverage Δ
cannon-go-tests-64	66.4% <ø> (ø)
unit	76.8% <ø> (+<0.1%)	⬆️

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see 4 files with indirect coverage changes

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 50e9f264d0

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".