chore: Updating GK -> opa versions

[JaydipGabani]

What this PR does / why we need it:
Adding a step in release workflow to fetch opa versions with gatekeeper release and update the opa-versions.md file. This PR eliminates the need of updating opa-versions.md after every release.

Here is an example of successful release PR - JaydipGabani#115.

Which issue(s) this PR fixes (optional, using fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when the PR gets merged):
Fixes #

Special notes for your reviewer:

[ritazh]

only need to add versions after v3.15.1

[JaydipGabani]

@ritazh Updated the versions. I also added a script to automate this process. Because of the script you will see there are tags and opa version added in the file that are older than 3.15.1.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.03%. Comparing base (3350319) to head (076c44f).
Report is 147 commits behind head on master.

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HEAD has 1 upload less than BASE

Flag	BASE (3350319)	HEAD (076c44f)
unittests	2	1

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3537      +/-   ##
==========================================
- Coverage   54.49%   48.03%   -6.46%     
==========================================
  Files         134      218      +84     
  Lines       12329    15167    +2838     
==========================================
+ Hits         6719     7286     +567     
- Misses       5116     7066    +1950     
- Partials      494      815     +321     

Flag	Coverage Δ
unittests	48.03% <ø> (-6.46%)	⬇️

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[sozercan]

🤗

[ritazh]

LGTM

Thanks for automating this!

[ritazh]

why is this PR adding opa version for 3.16 instead of 3.19?

[JaydipGabani]

why is this PR adding opa version for 3.16 instead of 3.19?

@ritazh wdym by 3.19?

[ritazh]

why is this PR adding opa version for 3.16 instead of 3.19?

@ritazh wdym by 3.19?

sorry I forgot to paste the link https://github.com/JaydipGabani/gatekeeper/pull/115/files#diff-7716142b7ef995ef204d6130d795699ce0509c9e4b060ba4375a7ad729194b58R10 this PR is bumping GK to 3.19 but the opa version update is for 3.16

[JaydipGabani]

why is this PR adding opa version for 3.16 instead of 3.19?

@ritazh wdym by 3.19?

sorry I forgot to paste the link https://github.com/JaydipGabani/gatekeeper/pull/115/files#diff-7716142b7ef995ef204d6130d795699ce0509c9e4b060ba4375a7ad729194b58R10 this PR is bumping GK to 3.19 but the opa version update is for 3.16

Sorry about confusion. I should have been clearer in the PR description. The confusion stems from a difference in the tags between my fork and the upstream Gatekeeper (GK) repository. For instance, my fork doesn't contain the 3.17 tags, so when I run git tag -l --sort=-v:refname, it doesn't return the 3.17 tags.

The PR I linked is a result of cutting the 3.18.0 release in my fork. Since the 3.18.0 tag doesn't exist in the upstream repo, running this command:
opa=$(curl https://raw.githubusercontent.com/open-policy-agent/gatekeeper/$tag/go.mod | grep /opa | awk '{print $2}')
fails to retrieve the OPA version for that tag. This is why the GK to OPA mappings for 3.17 and 3.18 are missing.

In short, the sample PR includes only the GK-to-OPA versions that are present in both the upstream repo and my fork, due to the tag differences between the two.

[JaydipGabani]

@maxsmythe PTAL.

[maxsmythe]

Thank you for automating this!