Fix case sensitivity for duplicate username creation

powerdnsadmin/models/user.py

@@ -408,7 +408,7 @@ class User(db.Model):
         Create local user witch stores username / password in the DB
         """
         # check if username existed
-        user = User.query.filter(User.username == self.username).first()
+        user = User.query.filter(User.username.lower() == self.username.lower()).first()
         if user:
             return {'status': False, 'msg': 'Username is already in use'}