Fixes the support for kwargs in `DiscourseEvent.trigger()` on Ruby 3, e.g.
```rb
DiscourseEvent.trigger(:before_system_message_sent, message_type: type, recipient: @recipient, post_creator_args: post_creator_args, params: method_params)
```
Fixes https://github.com/discourse/discourse-local-site-contacts
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
* DEV: Replace site_setting_saved DiscourseEvent with site_setting_changed
site_setting_saved is confusing for a few reasons:
- It is attached to the after_save of the ActiveRecord model. This is confusing because it only works 'properly' with the db_provider
- It passes the activerecord model as a parameter, which is confusing because you get access to the 'database' version of the setting, rather than the ruby setting. For example, booleans appear as 'y' or 'n' strings.
- When the event is called, the local process cache has not yet been updated. So if you call SiteSetting.setting_name inside the event handler, you will receive the old site setting value
I have deprecated that event, and added a new site_setting_changed event. It passes three parameters:
- Setting name (symbol)
- Old value (in ruby format)
- New value (in ruby format)
It is triggered after the setting has been persisted, and the local process cache has been updated.
This commit also includes a test case which describes the confusing behavior. This can be removed once site_setting_saved is removed.
