fix: #be clean up k8s api versions

backend/k8s/base/database/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - deployment.yaml

backend/k8s/base/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ./database

backend/k8s/base/webserver/ingress.yaml

-apiVersion: networking.k8s.io/v1
+apiVersion: extensions/v1beta1
 kind: Ingress
 metadata:
   name: ingress

backend/k8s/base/webserver/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - deployment.yaml

backend/k8s/overlays/dev/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ../../base

backend/k8s/overlays/stg/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
   - ../../base