feat(auth): add Authentik OIDC adapter

Refs #96

packages/auth/src/auth.ts

@@ -1,5 +1,6 @@
 import { betterAuth } from 'better-auth';
 import { drizzleAdapter } from 'better-auth/adapters/drizzle';
+import { genericOAuth } from 'better-auth/plugins';
 import type { Db } from '@mosaic/db';
 
 export interface AuthConfig {
@@ -10,6 +11,33 @@ export interface AuthConfig {
 
 export function createAuth(config: AuthConfig) {
   const { db, baseURL, secret } = config;
+  const authentikIssuer = process.env['AUTHENTIK_ISSUER'];
+  const authentikClientId = process.env['AUTHENTIK_CLIENT_ID'];
+  const authentikClientSecret = process.env['AUTHENTIK_CLIENT_SECRET'];
+  const plugins = authentikClientId
+    ? [
+        genericOAuth({
+          config: [
+            {
+              providerId: 'authentik',
+              clientId: authentikClientId,
+              clientSecret: authentikClientSecret ?? '',
+              discoveryUrl: authentikIssuer
+                ? `${authentikIssuer}/.well-known/openid-configuration`
+                : undefined,
+              authorizationUrl: authentikIssuer
+                ? `${authentikIssuer}/application/o/authorize/`
+                : undefined,
+              tokenUrl: authentikIssuer ? `${authentikIssuer}/application/o/token/` : undefined,
+              userInfoUrl: authentikIssuer
+                ? `${authentikIssuer}/application/o/userinfo/`
+                : undefined,
+              scopes: ['openid', 'email', 'profile'],
+            },
+          ],
+        }),
+      ]
+    : undefined;
 
   return betterAuth({
     database: drizzleAdapter(db, {
@@ -36,6 +64,7 @@ export function createAuth(config: AuthConfig) {
       expiresIn: 60 * 60 * 24 * 7, // 7 days
       updateAge: 60 * 60 * 24, // refresh daily
     },
+    plugins,
   });
 }