Removes the uniqueUsername route

Author: BoDonkey

CHANGELOG.md

@@ -6,6 +6,12 @@
 
 * Custom operations registered with `addCreateWidgetOperation` can now specify an `ifTypesIntersect` property containing an array of widget type names. If the area in question allows at least one, the operation is offered.
 
+### Fixes
+
+### Changes
+
+* Removes the non-functional `uniqueUsername` route from the `user` module
+
 ## 4.21.0 (2025-09-03)
 
 ### Adds

modules/@apostrophecms/user/index.js

@@ -186,22 +186,6 @@ module.exports = {
     self.addLegacyMigrations();
     await self.ensureSafe();
   },
-  apiRoutes(self) {
-    return {
-      post: {
-        async uniqueUsername(req) {
-          const username = self.apos.launder.string(req.body.username);
-          const user = self.find(req, { username }).project({
-            _id: 1,
-            username: 1
-          }).toObject();
-          if (user) {
-            throw self.apos.error('conflict');
-          }
-        }
-      }
-    };
-  },
   handlers(self) {
     return {
       beforeInsert: {