docs: Update docs around authentication to make them clearer where the route goes, and where the token is returned

documentation/topics/authenticate-with-json-api.md

@@ -2,30 +2,50 @@
 
 Authenticating with AshJsonApi requires a few things. The first thing to note is that this is not something that is provided for you out of the box by `ash_authentication`.
 
-You will need to
+You will need to:
 
 - connect the authentication action to a route manually
 - need to extract the resulting authentication token
 - set it as a header or as metadata to provide it to the client to use on future requests
 
+You may also need to add a policy bypass to your resource, to make the action accessible via a non-AshAuthenticationPhoenix liveview.
+
 ## The route
 
-In this example, we will use the standard `:sign_in_with_password` action that is created by `ash_authentication` under the hood, and we will return the token as top-level request metadata
+In this example, we will use the standard `:sign_in_with_password` action that is created by `ash_authentication` under the hood, and we will return the token as part of the response metadata.
 
 ```elixir
-# in your user resource
-routes do
-  # read actions that return *only one resource* are allowed to be used with
-  # `post` routes.
-
-  post :sign_in_with_password do
-    route "/sign_in/:id"
-
-    # given a successful request, we will modify the route to include the
-    # generated token
-    metadata(fn _subject, user, _request ->
-      %{token: user.__metadata__.token}
-    end)
+# In your User module
+defmodule <YourApp>.<YourDomain>.User do
+  json_api do
+    routes do
+      # Read actions that return *only one resource* are allowed to be used with
+      # `post` routes.
+      post :sign_in_with_password do
+        route "/sign_in"
+
+        # Given a successful request, we will modify the response to include the
+        # generated token
+        metadata fn _subject, user, _request ->
+          %{token: user.__metadata__.token}
+        end
+      end
+    end
   end
 end
 ```
+
+This will add the token to the `meta` key in a successful API response, eg.
+
+```json
+{
+  {
+  "data": {
+    "attributes": { ... },
+    ...
+  },
+  "meta": {
+    "token": "eyJhbGc..."
+  }
+}
+```