fix: update yaml validation to match kong behavior

[omegabytes]

Downgrades yaml package so that goks has behavioral parity with kong yaml validation.

[CLAassistant]

All committers have signed the CLA.

[GGabriele]

Do you know if there is any upstream GitHub Issue on the yaml project about why this doesn't work with v3 but it does with v1?

[mikefero]

@omegabytes Please clean up the description in this PR to reflect this change.

[aboudreault]

Should we standardize what we use for yaml across our different projects (if possible)? e.g. Kong/deck#800

[omegabytes]

Do you know if there is any upstream GitHub Issue on the yaml project about why this doesn't work with v3 but it does with v1?

I scanned the open + closed issues for go-yaml but didn't find a directly related issue.

[omegabytes]

Should we standardize what we use for yaml across our different projects (if possible)? e.g. Kong/deck#800

Strongly agree with standardizing, at least for yaml packages. Luckily downgrading to v1 was a simple fix (thanks @mikefero).

I've also considered standing up complete unit testing that asserts that yaml handling has behavioral parity with kong's yaml handling. That's a big task so I'd like to avoid it unless absolutely necessary. We'd probably need pretty exhaustive unit tests in both kong and in goks (and in deck, and so on).