New User/Blog activation email messages are difficult to customize

[mdawaffe]

The wpmu_signup_blog_notification_email and wpmu_signup_user_notification_email hooks allow plugins to customize the activation email messages.

No information about the actual signup is passed to the filter, however.

Attached adds extra parameters to those hooks and their related subject hooks.

[ryan]

(In [15552]) Pass more info to notification filters. Props mdawaffe. fixes #14743

[sboisvert]

I sadly lack the mental capacity to create diff files. (The Help Guide seems more geared on how to make trac work than how to submit to trac).

I really appreciate the additions made here. One thing I would like added is a filter on the headers. There may be a better way to achieve changing the email headers and if so I am more than willing to hear it. But I feel a filter on the headers could be useful.

I would suggest adding a change of line 656 to:

$message_headers = apply_filters( 'wpmu_signup_user_notification_headers',"From: \"{$from_name}\" <{$admin_email}>\n" . "Content-Type: text/plain; charset=\"" . get_option('blog_charset') . "\"\n",$from_name,$admin_email, $domain, $path,$meta);