FEAT(image-updater): add github-creds ExternalSecret

- Manage GitHub PAT via Vault
- Remove manual secret creation requirement

argocd-image-updater/manifests/secret.yaml

@@ -25,3 +25,26 @@ spec:
       remoteRef:
         key: zot
         property: PASSWORD
+---
+apiVersion: external-secrets.io/v1
+kind: ExternalSecret
+metadata:
+  name: github-creds
+  namespace: argocd
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    kind: ClusterSecretStore
+    name: vault-backend
+  target:
+    name: github-creds
+    creationPolicy: Owner
+  data:
+    - secretKey: username
+      remoteRef:
+        key: github
+        property: username
+    - secretKey: password
+      remoteRef:
+        key: github
+        property: password