[5.4] Improve defining email recipients for update notification

[chmst]

Follow-up for PR #45721

Summary of Changes

Until now, recipients of update notifications are defined as a comma separated list of email addresses.
This means: First find the email-addresses of super users, then maintain the list when super users leave or are added or when they change emailaddress.

This PR works like in AutoUpdate notification: #45721

All Super Users get the update notification. Additionally other user groups can be added. Recipients must be active and have the sendEmail Option allowed.

The Updatescript will remove the old email option from parameters in the table. If there were old entries, they will be deleted. These entries were a subset of super users, so there is no break.

Testing Instructions

1. Run the update script. The mysql script is tested, the postgresql script is generated by AI and needs a tester with these skills.

2. Make different users, different user groups, they can be empty, have super users not, have sendEmail activated or not and can be blocked or not.

3. Go to scheduled tasks and open the Update Notification Plugin. Check if user Groups can be added.

4. Testing if the email addresses now are correct is tricky.

Actual result BEFORE applying this Pull Request

Comma separated list of super users or the super user (id = 8) per default

Expected result AFTER applying this Pull Request

It is possible to select user groups from a list. Super Users are added per default and must notr be selected.

Link to documentations

Please select:

• Documentation link for docs.joomla.org: [(https://docs.joomla.org/J3.x:Plugin_Joomla_Update_Notification#Super_User_Email]

• No documentation changes for manual.joomla.org needed

[brianteeman]

Do I read this correct.

Before this PR a site owner could set a limited number of super users to receive this specific email but now all super users will receive the email.

If I read it correctly and this is the case then this is a change in behaviour on an existing site that should not happen in a minor release

[chmst]

I made this as draft, so we can discuss.
We should have equal behaviour here and for automaded update notifications.

If we don't want to inform all super users, then we could make a users selection of all users who have the super user rights or sendEmail option = "on".
On the one hand it is better if only one super user is responsible, on the other hand it could be that nobody gets a notification, as it is now when super users change.

I am ok with J6.0, release managers can decide.

[brianteeman]

My only concern is that this proposes a change of behaviour on existing sites with no notification

[travisrisner]

What if there is another parameter using a radio for "Send to list of email addresses" or "Send to user groups" (probably different wording). Both comma separated list and group selection fields can exist and be toggled with a showon. By default it keeps the comma separated list on so it doesn't break current installations, but still allows you to set the functionality to send to a group instead.