Validate YAML / JSON API values

[chrislovecnm]

In order to provide greater usability, we should have validation that does:

1. validate valid YAML before a kops execution, before a state store is created.
2. validate extra YAML values. Currently, we ignore extra stuff, we should warn and force the user to turn off warning like kubectl.
3. what am I missing? Validate different versioning? For instance when we move from v2 to v3?

[chrislovecnm]

Some notes from @liggitt

to see if you're dropping fields, you can decode into an unstructured object in addition to your struct type, then re-encode your struct and see if they are equal

1. get bytes to decode
2. decode into unstructured.Unstructured

• 2 and 3 should match
• if 3 has extra data, then you likely are using defaulting that set fields for the user
• if 3 has missing data, then the user specified fields not present in your struct
  that could be because they're writing to a newer version of kops, or because they typo-ed a field
• if you get strict about not dropping fields, older versions of kops will break if the user specifies a value that is unrecognized

We also just need to validate the file as valid YAML.

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-testing, kubernetes/test-infra and/or fejta.
/lifecycle stale

[blakebarnett]

/remove-lifecycle stale

[chrislovecnm]

/lifecycle frozen