docs: improve commerce modules [1/n] (#9498)

Improve and add docs for API Key, Auth, and Cart Modules

[1/n]

www/apps/resources/generated/sidebar.mjs

@@ -56,8 +56,8 @@ export const generatedSidebar = [
                 "loaded": true,
                 "isPathHref": true,
                 "type": "link",
-                "path": "/commerce-modules/api-key/relations-to-other-modules",
-                "title": "Relation to Modules",
+                "path": "/commerce-modules/api-key/links-to-other-modules",
+                "title": "Link to Modules",
                 "children": []
               }
             ]
@@ -538,6 +538,14 @@ export const generatedSidebar = [
             "title": "Examples",
             "children": []
           },
+          {
+            "loaded": true,
+            "isPathHref": true,
+            "type": "link",
+            "path": "/commerce-modules/cart/extend",
+            "title": "Extend Module",
+            "children": []
+          },
           {
             "loaded": true,
             "isPathHref": true,
@@ -572,8 +580,8 @@ export const generatedSidebar = [
                 "loaded": true,
                 "isPathHref": true,
                 "type": "link",
-                "path": "/commerce-modules/cart/relations-to-other-modules",
-                "title": "Relations to Other Modules",
+                "path": "/commerce-modules/cart/links-to-other-modules",
+                "title": "Links to Other Modules",
                 "children": []
               }
             ]