docs: add example for login flow

docs/flow/examples/login.md

@@ -0,0 +1,36 @@
+# Login Flow
+
+This document describes how a simple authentication flow can be created.
+
+This flow is created automatically when passbook is installed.
+
+1. Create an **Identification** stage
+
+    > Here you can select whichever fields the user can identify themselves with
+    > Select the Template **Default Login**, as this template shows the (optional) Flows
+    > Here you can also link optional enrollment and recovery flows.
+
+2. Create a **Password** stage
+
+    > Select the Backend you want the password to be checked against. Select "passbook-internal Userdatabase".
+
+3. Create a **User Login** stage
+
+    > This stage doesn't have any options.
+
+4. Create a flow
+
+    > Create a flow with the delegation of **Authentication**
+    > Assign a name and a slug. The slug is used in the URL when the flow is executed.
+
+5. Bind the stages to the flow
+
+    > Bind the **Identification** Stage with an order of 0
+    > Bind the **Password** Stage with an order of 1
+    > Bind the **User Login** Stage with an order of 2
+
+    ![](login.png)
+
+!!! notice
+
+    This flow can used by any user, authenticated and un-authenticated. This means any authenticated user that visits this flow can login again.