add validity check if user changes name in User Settings>Personal moi…

…nwiki#1707

docs/user/accounts.rst

@@ -15,7 +15,9 @@ by clicking the account creation button, and you will be presented with an accou
 The fields of this form are as follows:
 
 Name
- Your username on the wiki. Will appear in the history section of any wiki item which you edit. This is a required field.
+ Your username on the wiki.  Names must not contain "/",  ":", or "," characters, invisible unicode
+ characters, or leading or trailing whitespace characters. Embedded single space characters
+ are allowed.  This is a required field.
 
 Password
  Your password for logging into your new account. Remember to pick a strong password with a mix
@@ -55,7 +57,12 @@ Personal Settings
 Personal settings include wiki language and locale, username and alias.
 
 Name
- Your username, as it will appear on the wiki and in the history pages of wiki items which you edit.
+ Your username, as it will appear on the login form, the history pages of wiki items
+ which you edit, and in the footer of items you have edited. All of these places will be
+ rendered as links to your home page in the `users` namespace.
+ If desired, name may be a comma separated list of names. For example, if it is tedious
+ to type your long full name at login, you may create a short alias name: `JohnDoe, jd`.
+ Alias names are only useful at login.
 
 Display-Name
  The display name can be used to override your username, so you will still log in using your username

src/moin/apps/frontend/views.py

@@ -2447,6 +2447,14 @@ class UserSettingsUIForm(Form):
                                         (_("The username '{name}' is already in use.").format(name=name), "error")
                                     )
                                     success = False
+                                if not user.normalizeName(name) == name:
+                                    response["flash"].append(
+                                        (
+                                            _("The username '{name}' contains invalid characters").format(name=name),
+                                            "error",
+                                        )
+                                    )
+                                    success = False
                     if part == "notification":
                         if (
                             form["email"].value != flaskg.user.email