First follow-up to the feature introduced in #19034. We don't want to pollute main components like `chat-live-pane`, so we'll use a service to track and manage the state needed to display before-send warnings while composing a chat message.
We also move from acceptance tests to system specs.
* FEATURE: Enforce mention limits for chat messages
The first part of these changes adds a new setting called `max_mentions_per_chat_message`, which skips notifications when the message contains too many mentions. It also respects the `max_users_notified_per_group_mention` setting
and skips notifications if expanding a group mention would exceed it.
We also include a new component to display JIT warning for these limits to the user while composing a message.
* Simplify ignoring/muting filter in chat_notifier
* Post-send warnings for unsent warnings
* Improve pluralization
* Address review feedback
* Fix test
* Address second feedback round
* Third round of feedback
Co-authored-by: Joffrey JAFFEUX <j.jaffeux@gmail.com>
