Deprecate admin_created_user_subject()

[jeremyfelt]

In ​MU:1529, a wpmu_signup_user_notification_subject filter was added which called admin_created_user_subject() to set the subject of an invite email when a new user was added. A similar filter and function were added for the email content itself.

In the merge, [12722], the filter and function for the email were brought over into wp-admin/user-new.php, but only the function for the subject was brought over—not the filter.

It doesn't appear to have been missed. :)

The strange part about deprecating this is admin_create_user_subject() is currently defined only when wp-admin/user-new.php is accessed in multisite. Once deprecated, it will be loaded into memory more often. But, we really don't need it.

[jeremyfelt]

In 30005:

Deprecate admin_created_user_subject()

When admin_created_user_subjec() was merged from MU, the accompanying filter was left behind. As it has never been used by WordPress core, and is not an otherwise useful function, it can be deprecated.

Fixes #29915

[jeremyfelt]

After talking with @nacin last week about this, it looks like we can delete admin_created_user_subject() entirely.

It was previously only available on user-new.php in multisite and never used in MU as a callback to the original filter. At the worst, if a developer was reusing that filter configuration, they would see a notice.

[jeremyfelt]

In 30176:

Delete admin_created_user_subject() rather than deprecate

As it was never used as anything more than a callback to a filter before the MU merge, and is only available in user-new.php in multisite, it is safe to remove this function entirely.

Fixes #29915

[nacin]

Replying to jeremyfelt:

After talking with @nacin last week about this, it looks like we can delete admin_created_user_subject() entirely.

I just reviewed [30176] and was coming to this ticket to note I agreed with removing it. Now I'm also noting I don't remember that conversation from 6 weeks ago, so thank you for documenting it. :-)