Add auth and state access for terraform-authentik (#78)

## Summary
- K8s auth role for Woodpecker CI (`terraform-authentik` SA in `woodpecker` namespace)
- AppRole for local terraform runs
- Consul secret backend role (`terraform-authentik`, TTL 120/300)
- Consul ACL policy for `infra/terraform/authentik/` key prefix
- Vault policy granting both auth methods access to Consul creds

Reviewed-on: #78
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

config/auth_approle_role/approle/terraform_authentik.yaml

@@ -0,0 +1,9 @@
+token_ttl: 120
+token_max_ttl: 120
+bind_secret_id: false
+token_bound_cidrs:
+  - "10.10.12.200/32"
+  - "198.18.25.102/32"
+  - "198.18.26.91/32"
+  - "198.18.27.40/32"
+use_deterministic_role_id: true

config/auth_kubernetes_role/k8s/au/syd1/woodpecker_terraform_authentik.yaml

@@ -0,0 +1,7 @@
+bound_service_account_names:
+  - terraform-authentik
+bound_service_account_namespaces:
+  - woodpecker
+token_ttl: 600
+token_max_ttl: 600
+audience: https://kubernetes.default.svc.cluster.local

config/consul_secret_backend_role/consul_root/au/syd1/terraform-authentik.yaml

@@ -0,0 +1,5 @@
+consul_roles:
+  - terraform-authentik
+ttl: 120
+max_ttl: 300
+datacenters: []