Let one notification address several recipients (#7782)

* feat(notify): let one notification address several recipients

Symfony calls a channel once per recipient, so a caller that needs a single
message sent to several people could not express it. The email 'to' option
folds the extra addresses into the same mailer() call and drops any that
match the recipient.

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

* fix(notify): compare the local part of an address exactly

RFC 5321 leaves local part case to the receiving host, so folding the whole
address deduplicated OPS@example.com and ops@example.com into one mailbox.
Only the domain folds now.

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

---------

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

CHANGELOG

@@ -164,6 +164,7 @@ Cacti CHANGELOG
 -issue#7861: Repair confirmed poller, database, automation, export, filtering, theme, and arithmetic defects
 -issue#7751: Declare the translation helper before the disabled-i18n fallback returns
 -issue#7476: Escape path_boost_log before it reaches the Boost debug shell redirect
+-issue#7782: Allow one notification to address several recipients through the email 'to' option
 -issue#7473: Escape path_rrdcheck_log before it reaches the rrdcheck poller shell redirect
 -issue#7469: Escape path_php_binary before it reaches shell_exec in test_data_source
 -issue#7466: Escape path_stderrlog before it reaches the poller stderr shell redirect