Ingress V1: Parse Ingress V1 entries from Store.

[mflendrich]

closes #789
closes #791

This PR:

• extends parser.Build() with fromIngressV1(): as of now, parser.Build includes v1 ingresses in the resulting KongState. There are three bits that we still need after this PR for full KEP compatibility:
  • ingress v1: parse ingress class field in Ingress v1 resource #790 is not done yet - with this PR, KIC requires v1 ingresses to have an annotation, and disregards the spec.ingressClass field
  • ingress V1: implement status sync #830: the KEP expects us to support 3 ways of defining a backend for an ingress path 😓
    • by service name and port number - done
    • by service name and port name - not done
    • by service name (expecting the service to have only one port) - not done
  • Ingress V1: wildcard should match only a single subdomain level #837: wildcard host matching matches one or more subdomain levels (a.foo.com and a.b.foo.com both match *.foo.com, where the KEP expects only the former to match)
• makes some drive-by cleanups (see individual commits)

After this PR, KIC practically supports Ingress V1 (in a scope specified above).

Also, fromIngressV1 is unit-tested but there's no high level test for parser.Build actually handling ingressv1 correctly. I'd like to spark a discussion about the right way to test this change (on a higher level than unit testing).

Notes to reviewers:

• consider reviewing commit by commit
• consider not squashing

[rainest]

Based on my work in #843, I think this is reasonably good to go. There are issues elsewhere (raised in #843), but not with these changes, more things alongside them that were in the controller before and whose limitations are now becoming apparent.

+1 on most of Harry's comments, but I believe they've now been addressed. I'll wait for his follow-up if he has any remaining items that we should continue to discuss here.

[hbagdi]

I'm still not sure about route priorities. They come into effect only if there is a regex route (they don't have any effect for regular paths).

Let's revisit this later. For most users, this is intuitive enough that it should not cause problems. Famous last words.