Fix OIDC test

[cpanato]

Summary

The test was missing some new flags and also the certificate that we use for self signing expired.

This PR update/fix the following things:

• use cosign build from the head and not from a release
• add a script to sign the digests and not the tags
• update the test script and update the flags
• regenerate the certificate because the previous one expired, now it is valid for 10 years
• add doc on how to regenerate a certificate in case we need it again :)
• enable go cache

test execution in the forked repo:

• https://github.com/cpanato/cosign/runs/7217059292?check_suite_focus=true
• and a subsequent run with cache: https://github.com/cpanato/cosign/runs/7217338096?check_suite_focus=true

Release Note

NONE

Documentation

NONE

[cpanato]

it uses https://rekor.sigstore.dev/api/v1/log/entries should we point to the staging env?

[priyawadhwa]

it uses https://rekor.sigstore.dev/api/v1/log/entries should we point to the staging env?

+1! I think it would be good to test against more recent versions of rekor before we update prod

[cpanato]

it uses https://rekor.sigstore.dev/api/v1/log/entries should we point to the staging env?

+1! I think it would be good to test against more recent versions of rekor before we update prod

ok, we can do it in a follow up, then we can validate if this is working as expected :)

[codecov-commenter]

Codecov Report

Merging #2050 (7d16021) into main (4ba8b6a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2050   +/-   ##
=======================================
  Coverage   26.22%   26.22%           
=======================================
  Files         128      128           
  Lines        7539     7539           
=======================================
  Hits         1977     1977           
  Misses       5307     5307           
  Partials      255      255           

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[priyawadhwa]

💯