add target group policy controller and status updates

[mikhail-aws]

Note:
Add TargetGroupPolicy controller. Controller validate targetRef and update status. TargetGroup builder applies only Accepted and TargetRefNotFound policies. TargetRefNotFound is safe to apply, it means policy was created before TG.
I have to update CRD because Status wasnt there fully. Users need to re-apply CRD after this change.

Tested manually:

• Create policy before TG, after TG was created checked policy applied
• Create multiple conflicting policies and checked none of them applied
• Created policy and TG, then created conflicting policy. Checked second conflicting policy didnt override first one

We should refactor our PolicyAttachment code, right now every Policy CRD implements same validation and status update logic. Need to create general purpose PolicyAttachment handler for validation and status update. #508

close #440

[solmonk]

I have to update CRD because Status wasnt there fully. Users need to re-apply CRD after this change.

So when the controller upgrades without CRD upgrade, it will disregard all TGPs and turn HTTP2 TGs into HTTP1 TGs, it seems. It is a bit worrying behavior to me actually. Should we add a fallback, like consider TGPs with no status as valid? Or, should we increment TGP version so that only old TGPs with no status are valid?

[zijun726911]

I feel like that would be a better policyInfo naming:

type policyInfo struct {
	policyList core.PolicyList
	targetRefGroup      gwv1beta1.Group
	targetRefKind       gwv1beta1.Kind
}

[zijun726911]

Seems this function actually do: GetAttachedPoliciesFilterByAcceptedConditionReasons , would be good if we can add comments or change function name to make people more easily know this function's behaviour.

[mikhail-aws]

removed and refactored for conflict resolution logic

[zijun726911]

I have to update CRD because Status wasnt there fully. Users need to re-apply CRD after this change.

So when the controller upgrades without CRD upgrade, it will disregard all TGPs and turn HTTP2 TGs into HTTP1 TGs, it seems. It is a bit worrying behavior to me actually. Should we add a fallback, like consider TGPs with no status as valid? Or, should we increment TGP version so that only old TGPs with no status are valid?

Just provide upgrade instructions and do this breaking change before v1.0.0 looks fine for me

[solmonk]

The approach overall LGTM.