Add support for `k8gb.io/dns-ttl-seconds` and `k8gb.io/splitbrain-threshold-seconds` strategy annotations

[somaritane]

dnsTtlSeconds and splitBrainThresholdSeconds strategy spec fields shoud be wired to gslb custom resource,
when one is created out of Ingress object with respective annotations.

Following annotation names are suggested:

• splitBrainThresholdSeconds: k8gb.io/splitbrain-threshold-seconds
• dnsTtlSeconds: k8gb.io/dns-ttl-seconds

[ytsarev]

It smells like recreation of the whole spec on annotation level. I am not sure we have to go down this road

[somaritane]

What should be criteria to decide which spec option is supported by Ingress annotations, and which one is not?
I feel like at least strategy related options should be wired.
If we don't want to wire them - does it mean that we're not considering Ingress with annotation as full-fledged citizen of k8gb configuration along with gslb custom resource?

[ytsarev]

@somaritane the initial idea of annotation approach was to just bound existing Ingress with new Gslb resource, not full control over this resource.

[kuritka]

Hello, I understand initial approach, but when I imagine the customer's view, he will probably expect both approaches to be compatible.

[ytsarev]

no objections, but it's gonna be fun when/if spec gets larger