feat: manage gitadmin token (#74)

- add approle for terraform-git
- add policy to read gitadmin token
- update access to the terraform-git consul token

---------

Co-authored-by: Ben Vincent <ben@unkin.net>
Reviewed-on: #74

policies/consul_root/au/syd1/creds/terraform-git.yaml

@@ -5,5 +5,7 @@ rules:
       - read
 
 auth:
+  approle:
+    - terraform_git
   k8s/au/syd1:
     - woodpecker_terraform_git

policies/kv/service/gitea/gitadmin/tokens/terraform-git/read.yaml

@@ -0,0 +1,12 @@
+# Allow reading Gitea admin token
+---
+rules:
+  - path: "kv/data/service/gitea/gitadmin/tokens/terraform-git"
+    capabilities:
+      - read
+
+auth:
+  approle:
+    - terraform_git
+  k8s/au/syd1:
+    - woodpecker_terraform_git