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/configuration.yml

@@ -10,6 +10,23 @@ authentication_backend:
     url: ldaps://pyrocufflink.blue
     user: CN=svc.authelia,CN=Users,DC=pyrocufflink,DC=blue
 
+identity_providers:
+  oidc:
+    clients:
+    - id: e20a50c2-55eb-4cb1-96ce-fe71c61c1d89
+      description: Jenkins
+      secret: >-
+        $argon2id$v=19$m=65536,t=3,p=4$qoo6+3ToLbsZOI/BxcppGw$srNBfpIHqpxLh+VfVNNe27A1Ci9dCKLfB8rWXLNkv44
+      redirect_uris:
+      - https://jenkins.pyrocufflink.blue/securityRealm/finishLogin
+      scopes:
+      - openid
+      - groups
+      - profile
+      - email
+      - offline_access
+      authorization_policy: one_factor
+
 log:
   level: trace