ci: least privileged GITHUB_TOKEN permissions

[ricardoapl]

What this PR does / why we need it:

The GITHUB_TOKEN is an automatically generated secret to make authenticated calls to the GitHub API. GitHub recommends setting minimum token permissions for the GITHUB_TOKEN, otherwise attackers may use a compromised token with write access to, for example, push malicious code into the project.

Found in CLOMonitor Checks and OpenSSF Scorecard Report.

How does this change affect the cardinality of KSM:

Does not change cardinality

Which issue(s) this PR fixes:

Part of #2274

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[mrueg]

If #2398 is getting merged, will this workflow work with only read permissions?

[ricardoapl]

If #2398 is getting merged, will this workflow work with only read permissions?

That's a good point, the workflow will not work with read only permissions then.

I suggest we keep default top-level permissions to read-only, but add contents: write permissions at job-level to #2398.

Although perhaps unlikely, there's a chance that a new job is added to this workflow, and its permissions could be left undefined because of human error.

What do you think?

[mrueg]

Sounds good to me, let's mark this read-only for now.

/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mrueg, ricardoapl

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