Put the artifactapi web UI behind Authentik oauth2-proxy (#456)

The artifactapi web UI is open to anyone who can reach the host. Front it with Authentik SSO gated on akP-artifactapi-admin, while leaving the package-manager surfaces (/api/v1, /api/v2, /v2 docker registry, /terraform, /.well-known) untouched — dnf, containerd mirrors, buildah, terraform and CI publish steps cannot do a browser flow.

- Add the oauth2-proxy ConfigMap, Deployment, Service and VMPodScrape.
- Add the oauth-credentials VaultStaticSecret.
- Point the api-route /ui rule at oauth2-proxy and add a /oauth2 rule; the catch-all / rule still goes straight to the api Service on both listeners.

Requires terraform-authentik #34 applied and the Vault kv seed first.

Reviewed-on: #456
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>

apps/base/artifactapi/oauth2-proxy-deployment.yaml

@@ -0,0 +1,93 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: oauth2
+  namespace: artifactapi
+  annotations:
+    configmap.reloader.stakater.com/auto: "true"
+    secret.reloader.stakater.com/reload: "oauth-credentials"
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app: oauth2
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+    type: RollingUpdate
+  template:
+    metadata:
+      labels:
+        app: oauth2
+    spec:
+      serviceAccountName: default
+      automountServiceAccountToken: false
+      securityContext:
+        runAsNonRoot: true
+        runAsUser: 65532
+        runAsGroup: 65532
+        fsGroup: 65532
+        seccompProfile:
+          type: RuntimeDefault
+      containers:
+        - name: oauth2-proxy
+          image: quay.io/oauth2-proxy/oauth2-proxy:v7.15.3
+          imagePullPolicy: IfNotPresent
+          ports:
+            - containerPort: 4180
+              name: http
+              protocol: TCP
+            - containerPort: 44180
+              name: metrics
+              protocol: TCP
+          envFrom:
+            - configMapRef:
+                name: artifactapi-oauth2-env
+                optional: false
+          env:
+            - name: OAUTH2_PROXY_CLIENT_ID
+              valueFrom:
+                secretKeyRef:
+                  name: oauth-credentials
+                  key: client_id
+            - name: OAUTH2_PROXY_CLIENT_SECRET
+              valueFrom:
+                secretKeyRef:
+                  name: oauth-credentials
+                  key: client_secret
+            - name: OAUTH2_PROXY_COOKIE_SECRET
+              valueFrom:
+                secretKeyRef:
+                  name: oauth-credentials
+                  key: cookie_secret
+          livenessProbe:
+            httpGet:
+              path: /ping
+              port: http
+            initialDelaySeconds: 10
+            periodSeconds: 30
+            timeoutSeconds: 5
+            failureThreshold: 3
+          readinessProbe:
+            httpGet:
+              path: /ready
+              port: http
+            initialDelaySeconds: 5
+            periodSeconds: 10
+            timeoutSeconds: 5
+            failureThreshold: 3
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop:
+                - ALL
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 500m
+              memory: 256Mi
+      restartPolicy: Always