Follow up to 098ab29d41. Since
we just used a `cattr_reader` on `About` this was not safe
for multisite, since some sites could have the chat plugin
enabled and some may not. Using `DiscoursePluginRegistry` gets
around this issue, and makes it so the chat stats only show
for a site if `chat_enabled` is true.
This commit introduces a new plugin API to register
a group of stats that will be included in about.json
and also conditionally in the site about UI at /about.
The usage is like this:
```ruby
register_about_stat_group("chat_messages", show_in_ui: true) do
{
last_day: 1,
"7_days" => 10,
"30_days" => 100,
count: 1000,
previous_30_days: 120
}
end
```
In reality the stats will be generated any way the implementer
chooses within the plugin. The `last_day`, `7_days`, `30_days,` and `count`
keys must be present but apart from that additional stats may be added.
Only those core 4 stat keys will be shown in the UI, but everything will be shown
in about.json.
The stat group name is used to prefix the stats in about.json like so:
```json
"chat_messages_last_day": 2322,
"chat_messages_7_days": 2322,
"chat_messages_30_days": 2322,
"chat_messages_count": 2322,
```
The `show_in_ui` option (default false) is used to determine whether the
group of stats is shown on the site About page in the Site Statistics
table. Some stats may be needed purely for reporting purposes and thus
do not need to be shown in the UI to admins/users. An extension to the Site
serializer, `displayed_about_plugin_stat_groups`, has been added so this
can be inspected on the client-side.
* DEV: small refactor of the category_moderators method
Used `index_by(&:id)` instead of `map { |u| [u.id, u] }.to_h` thanks to @cvx's recommendation.
Also renamed the `moderators` variable to not clash with method of the same name.
In the about page, we list a certain number of category moderators.
This rewrites the SQL query used to retrieve the most recent category moderators in order
to perform better with a large number of users/categories/category moderators.
TIL: you can ORDER BY inside an ARRAY_AGG in postgres
TIL: you can slide ARRAYS in postgres
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
