Why this change?
This is a follow-up to 86b2e3aa3e.
Basically, we want to allow people to select more than 1 category as well.
What does this change do?
1. Change `type: category` to `type: categories` and support `min` and `max`
validations for `type: categories`.
2. Fix the `<SchemaThemeSetting::Types::Categories>` component to support the
`min` and `max` validations and switch it to use the `<CategorySelector>` component
instead of the `<CategoryChooser>` component which only supports selecting one category.
Why this change?
On the `/admin/customize/themes/<:id>` route, we allow admins to edit
all settings via a settings editor. Prior to this change, trying to edit
and save a typed objects theme settings will result in an error on the
server.
Why this change?
When creating a new theme setting that does not have a corresponding row
in the `theme_settings` table, we end up writing to the database twice
because `ActiveRecord::Base#save!` is called once before the `value`
or `json_value` column is updated again with another database query with
another call to `ActiveRecord::Base#save!`.
What does this change do?
Adds the column to be updated to argument for the `ActiveRecord::Base#create!`
method call so that we only have one write query to the database.
Why this change?
The `/admin/customize/themes/:id/schema/name` route is a work in
progress but we want to be able to start navigating to it from the
`/admin/customize/themes/:id` route.
What does this change do?
1. Move `adminCustomizeThemes.schema` to a child route of
`adminCustomizeThemes.show`. This is because we need the model
from the parent route and if it isn't a child route we end up
having to load the theme model again from the server.
1. Add the `objects_schema` attribute to `ThemeSettingsSerializer`
1. Refactor `SiteSettingComponent` to be able to render a button
so that we don't have to hardcode the button rendering into the
`SiteSettings::String` component
