oauth diagram

Author: chdeskur

fern/products/docs/pages/authentication/oauth-diagram.mdx

@@ -0,0 +1,32 @@
+```mermaid
+sequenceDiagram
+    participant U as User
+    participant F as Fern Docs
+    participant A as OAuth2 Provider
+
+    U->>F: Visit restricted page
+    F->>F: Check fern_token cookie
+    
+    alt Cookie exists
+        F->>F: Decode cookie
+        F->>F: Verify authentication credentials
+        Note over F: Attempt to refresh the token, if expired
+        
+        alt User is properly authenticated
+            F->>U: Show restricted content
+        else User is not properly authenticated
+            F->>U: User is shown a 404 page
+        end
+    else No cookie
+        F->>A: Redirect to `/authenticate` endpoint
+        A->>U: User authenticates
+        U->>F: Authorization code is returned
+        F->>A: Redirect to `/token` endpoint
+        A->>A: Validate token request
+        A->>F: Send authenticated access token
+        F->>F: Set fern_token cookie
+        F->>F: Verify authentication credentials
+        F->>U: Show restricted content
+    end
+```
+