feat: document login hints feature (#1512)

* feat: document login hints feature

* docs: login hints

---------

Co-authored-by: Vincent Kraus <[email protected]>

docs/identities/sign-in/login-hint.mdx

@@ -0,0 +1,42 @@
+---
+id: login-hint
+title: Display login hint for duplicate identifiers
+sidebar_label: Login hints
+slug: login-hint
+---
+
+:::info
+
+Login hints are enabled by default for newly created Ory Network Projects.
+
+:::
+
+When users attempt to sign up with an identifier (username, email address etc.) which has previously been registered, they will be
+presented an error explaining that an identity is already created for that identifier.
+
+If you have a number of different sign-in methods configured (say username and password plus one or more social sign-in
+providers), its common for users users to not remember with which provider they initially signed up. This can lead to errors when
+attempting to log in with the wrong method.
+
+To address this, Ory Identities provides "login hints." Login hints provide a message what authentication method is available for
+the users identifier when they choose a method for which an identity already exists.
+
+To enable login hints edit your Ory Identities configuration directly or use the following CLI command:
+
+```bash
+ory list projects # to get the project id
+
+ory patch project ${project_id} \
+  --replace '/services/identity/config/selfservice/flows/registration/login_hints=true'
+```
+
+![Ory Account Experience with login hint](./_static/login-hint.png)
+
+:::info
+
+This behavior improves the sign-in experience for your users, but comes at the cost of exposing information about which sign-in
+mehods a particular account identifier has associated with it.
+
+Disable this feature if account enumeration attacks are a risk factor in your threat model.
+
+:::

src/sidebar.js

@@ -95,6 +95,7 @@ module.exports = {
             },
             "identities/sign-in/check-session",
             "identities/sign-in/actions",
+            "identities/sign-in/login-hint",
           ],
         },
         {