authelia: Enable OIDC provider

Authelia can act as an Open ID Connect identity provider.  This allows
it to provide authentication/authorization for other applications
besides those inside the Kubernetes cluster using it for Ingress
authentication.

To start with, we'll configure an OIDC client for Jenkins.

authelia/authelia.yaml

@@ -81,6 +81,10 @@ spec:
           value: /run/authelia/secrets/session.secret
         - name: AUTHELIA_STORAGE_ENCRYPTION_KEY_FILE
           value: /run/authelia/secrets/storage.encryption_key
+        - name: AUTHELIA_IDENTITY_PROVIDERS_OIDC_HMAC_SECRET_FILE
+          value: /run/authelia/secrets/oidc.hmac_secret
+        - name: AUTHELIA_IDENTITY_PROVIDERS_OIDC_ISSUER_PRIVATE_KEY_FILE
+          value: /run/authelia/secrets/oidc.issuer_private_key
         startupProbe:
           httpGet:
             port: 9091