Gatewayclass controller

[pleshakov]

Adds a Controller for GatewayClass resource. This is a PoC, to be discussed

gkubectl logs nginx-gateway-5d4f4c7db7-h5cdc -c nginx-gateway
{"level":"info","ts":1636415100.3172226,"caller":"gateway/main.go:46","msg":"Starting NGINX Gateway","version":"0.0.1","commit":"177960476d204f8f1908448e112b668bde741ad2","date":"2021-11-08T23:43:06Z"}
{"level":"info","ts":1636415100.3616116,"logger":"controller-runtime.metrics","msg":"metrics server is starting to listen","addr":":8080"}
{"level":"info","ts":1636415100.3667648,"caller":"gateway/main.go:79","msg":"Starting manager"}
{"level":"info","ts":1636415100.3714108,"msg":"starting metrics server","path":"/metrics"}
{"level":"info","ts":1636415100.3717198,"logger":"controller.gatewayclass","msg":"Starting EventSource","reconciler group":"gateway.networking.k8s.io","reconciler kind":"GatewayClass","source":"kind source: /, Kind="}
{"level":"info","ts":1636415100.3718565,"logger":"controller.gatewayclass","msg":"Starting Controller","reconciler group":"gateway.networking.k8s.io","reconciler kind":"GatewayClass"}
{"level":"info","ts":1636415100.4728386,"logger":"controller.gatewayclass","msg":"Starting workers","reconciler group":"gateway.networking.k8s.io","reconciler kind":"GatewayClass","worker count":1}
{"level":"info","ts":1636415100.4732518,"caller":"implementation/gatewayclass.go:25","msg":"Processing GatewayClass resource","name":"nginx"}
{"level":"error","ts":1636415125.7124593,"caller":"implementation/gatewayclass.go:29","msg":"GatewayClass resource was removed","name":"nginx","stacktrace":"github.com/nginxinc/nginx-gateway-kubernetes/internal/implementation.(*gatewayClassImplementation).Remove\n\tgith
ub.com/nginxinc/nginx-gateway-kubernetes/internal/implementation/gatewayclass.go:29\ngithub.com/nginxinc/nginx-gateway-kubernetes/internal/sdk.(*gatewayClassReconciler).Reconcile\n\tgithub.com/nginxinc/nginx-gateway-kubernetes/internal/sdk/gatewayclass_controller.go:53\
nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile\n\tsigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:114\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler\n\tsigs.k8s.io/cont
[email protected]/pkg/internal/controller/controller.go:311\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem\n\tsigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:266\nsigs.k8s.io/controller-runtime
/pkg/internal/controller.(*Controller).Start.func2.2\n\tsigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:227"}