Add an optional way to override timestamp format in json logs

[raj-saxena]

Description

I opened an issue earlier where @jon-whit agreed (#1326 (comment)) that moving towards ISO8601 is a better option.
As such, I raised a PR earlier #1329 where @jon-whit raised a valid point (#1329 (comment)) that we should not break compatibility for any existing users.

I have made the changes accordingly in this PR making ISO8601 as the default format while giving an option to enable the older option too if someone wants that. I understand that this could be a breaking change for some users but in the long run, I believe, this would be a step in the right direction. (adjusted to keep Unix as default after review comments)

Verified visually (since there was no test for this)

References

Fixes #1326 while addressing the comment from @jon-whit
#1329 (comment)

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected - provided visual evidence

[jon-whit]

Going to close #1329 in favor of this.

[miparnisari]

Like Jon said, let's keep the backward compatibility. Otherwise lgtm. We'll have to think where to add a test for this. TestCheckLogs already asserts on some fields logged, but I fear that test is becoming too bloated

[jon-whit]

Default needs to be Unix.

[raj-saxena]

@jon-whit @miparnisari I have pushed a commit defaulting to Unix format for json. I have updated the description and the screenshot in the PR too.
Please note that there's no way with the current change to have Unix for text format, but it also isn't something in the scope of the linked issue or being asked for right now.

[jon-whit]

@raj-saxena left one last comment. Looks good otherwise. Thanks!

[raj-saxena]

Updated the PR @jon-whit. Let's move this forward 🙏🏼