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
Previously theme setting descriptions were defined in the `settings.yml` file like this:
```
setting_name:
default: "My Default Value"
description:
en: "English description"
fr: "French description"
```
This commit allows developers to store the localised descriptions in the theme locale files instead:
```
en:
theme_metadata:
description: Theme Description
settings:
setting_name: "The localised description for setting_name"
```
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
Alan Guo Xiang Tan
David Taylor
Penar Musaraj
Sam Saffron
Joffrey JAFFEUX
OsamaSayegh