'allow_user_to_change_display_name' only affecting 'display name' not 'email address'

[jbrrrr]

As suggested in the closed #642

We need an option to disable change of display name without disabling the possibility to change the email address.

(Why do we need this?
for example:
Users (school) change their display names - make 'funny' things with shared content - rechange their name again - in activity log is a wrong name, and a wrong user is blamed...
Not good - but the users need to be able to change their email address by themselves)

'allow_user_to_change_display_name' = false should only affect display name.

Another setting
'allow_user_to_change_email_address'
could do the same for the email address.

Thanks for reevaluation.

[kesselb]

For the record

• Don't allow the user to set fields they can't see #5223 (comment)
• Don't allow the user to set fields they can't see #5223 (comment)
• Cannot set admin's e-mail address #13127

[theronakpatel]

@kesselb @MAXOUXAX @jbrrrr Any progress here ? I need this urgently. Is there any MR for this issue ?

I want : Another setting 'allow_user_to_change_email_address' could do the same for the email address.

[theronakpatel]

I added new MR: #40796