feat(documentation): Added authentik readme content and example helm values file

Authentik/README.md

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+# Authentik
+Authentik provides a single-sign-on service (SSO) that allows you to login to many different services using the same account. It provides LDAP, OIDC, OAUTH2, and other authentication endpoints. It is highly configurable (to the point of being quite complex). I used their helm chart ([found here](https://docs.goauthentik.io/install-config/install/kubernetes/)) to deploy mine. I may create a proper kubernetes deployment in the future if people want that, but the helm chart has worked perfectly fine for me. I have left an example values file here which is based on the one I used for my own deployment, but you are probably best off following the official documentation.

Authentik/values.yml

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+authentik:
+  secret_key: <secret key>
+  # This sends anonymous usage-data, stack traces on errors and
+  # performance data to sentry.io, and is fully opt-in
+  error_reporting:
+    enabled: false
+  postgresql:
+    password: <database password>
+
+server:
+  ingress:
+    # Specify kubernetes ingress controller class name
+    ingressClassName: traefik
+    enabled: true
+    hosts:
+      - <authentik hostname>
+    annotations:
+      cert-manager.io/cluster-issuer: "letsencrypt-production"
+    tls:
+      - hosts:
+          - <authentik hostname>
+        secretName: authentik-tls
+
+postgresql:
+  enabled: true
+  auth:
+    password: <database password>