fix(GRO-693): add UAT Terraform infrastructure with correct GitRepository

- Add terraform workspace at apps/overlays/uat/terraform/ (backend.tf,
  main.tf, variables.tf, users.tf, imports.tf, terraform.tfvars)
- Add Terraform CRD (authentik-terraform.yaml) with correct path
  ./apps/overlays/uat/terraform relative to groombook/app repo root
- Add GitRepository CRD (gitrepository-groombook.yaml) pointing to
  groombook/app at fix/gro-844-network-policy branch (NOT groombook/infra
  which no longer exists)
- Add kustomization.yaml to tie it together

Root cause: the GitRepository was pointing to https://github.com/groombook/infra
which no longer exists, and the terraform files were not committed to the
current repository at the correct path.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/overlays/uat/gitrepository-groombook.yaml

@@ -0,0 +1,19 @@
+---
+apiVersion: source.toolkit.fluxcd.io/v1
+kind: GitRepository
+metadata:
+  name: groombook
+  namespace: groombook-uat
+  labels:
+    app.kubernetes.io/name: groombook
+    app.kubernetes.io/part-of: groombook
+    app.kubernetes.io/env: uat
+spec:
+  interval: 15m
+  provider: github
+  ref:
+    branch: fix/gro-844-network-policy
+  secretRef:
+    name: cpfarhood-k8s
+  timeout: 60s
+  url: https://github.com/groombook/app