add vault auth for encapi

encapi (the new Postgres-backed Puppet ENC replacing Cobbler) runs in k8s and
reads its secrets from Vault via the Kubernetes auth backend. Grant its pods
that access, mirroring artifactapi.

- add k8s auth role encapi (binds SA default in namespace encapi, mount k8s/au/syd1)
- add vault policy kv/service/encapi/environment/read
- add vault policy kv/service/encapi/postgres-password/read

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

@@ -0,0 +1,7 @@
+bound_service_account_names:
+  - default
+bound_service_account_namespaces:
+  - encapi
+token_ttl: 600
+token_max_ttl: 600
+audience: vault

policies/kv/service/encapi/environment/read.yaml

@@ -0,0 +1,10 @@
+# Allow reading environment variables for encapi
+---
+rules:
+  - path: "kv/data/service/encapi/environment"
+    capabilities:
+      - read
+
+auth:
+  k8s/au/syd1:
+    - encapi

policies/kv/service/encapi/postgres-password/read.yaml

@@ -0,0 +1,10 @@
+# Allow reading environment vars for postgres/encapi
+---
+rules:
+  - path: "kv/data/service/encapi/postgres-password"
+    capabilities:
+      - read
+
+auth:
+  k8s/au/syd1:
+    - encapi