Grant the vault deployer auth/oidc and identity group capabilities (#148)

## Why

AppRole capabilities are fixed at login, so the deployer needs `auth/oidc/*` and identity-group grants in an apply that precedes the one creating those resources.

## How

- Add `policies/auth/oidc/admin.yaml`: full `auth/oidc/*` administration (mount config and login roles), mirroring `policies/auth/ldap/admin.yaml`.
- Add `policies/identity/group/admin.yaml`: manage external identity groups, group aliases and `identity/lookup/group`, on both the collection and per-id endpoints.
- Grant both policies to the `tf_vault` approle and the `woodpecker_terraform_vault` k8s role.

Apply before #147.

Reviewed-on: #148
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

policies/auth/oidc/admin.yaml

@@ -0,0 +1,19 @@
+# Allow full administration of the OIDC auth backend (mount config and login
+# roles), mirroring policies/auth/ldap/admin.yaml. sys/auth/* already covers
+# enabling the mount itself; this covers writing auth/oidc/config and
+# auth/oidc/role/*.
+---
+rules:
+  - path: "auth/oidc/*"
+    capabilities:
+      - create
+      - update
+      - read
+      - delete
+      - list
+
+auth:
+  approle:
+    - tf_vault
+  k8s/au/syd1:
+    - woodpecker_terraform_vault

policies/identity/group/admin.yaml

@@ -0,0 +1,38 @@
+# Allow the deployer to manage external identity groups and their aliases, which
+# is how OIDC group membership (the ak_groups claim) maps onto Vault policies.
+# Both the collection endpoints and the per-id endpoints are needed: create posts
+# to identity/group, subsequent reads and updates address identity/group/id/<id>.
+---
+rules:
+  - path: "identity/group"
+    capabilities:
+      - create
+      - update
+  - path: "identity/group/*"
+    capabilities:
+      - create
+      - update
+      - read
+      - delete
+      - list
+  - path: "identity/group-alias"
+    capabilities:
+      - create
+      - update
+  - path: "identity/group-alias/*"
+    capabilities:
+      - create
+      - update
+      - read
+      - delete
+      - list
+  - path: "identity/lookup/group"
+    capabilities:
+      - create
+      - update
+
+auth:
+  approle:
+    - tf_vault
+  k8s/au/syd1:
+    - woodpecker_terraform_vault