FEATURE: Add group and category restrictions to house ads (#205)

# Description

This PR adds the ability to apply **group** and **category** restrictions to a **house ad**.

# What is included
- In order to get the group and category selectors to work within `admin/assets/javascripts/discourse/controllers/admin-plugins-house-ads-show.js` I needed to modernize the file. 
- I dropped the `bufferedProperty` implementation in favor of a vanilla ember approach
- I added `category_ids` and `group_ids` to our house ads model
- I added tests for group / category restrictions
- I added a preview button to display the house ad
- `/site.json` would return a object called `house_creatives` and a list of key value pairs that matched the ad name with the html, like so:
```js
{ AD_KEY: ad.html }
```
I need access to the category ids on the client to conditionally render the house ads so the new format will be: 
```js
{ AD_KEY: { html: ad.html, category_ids: ad.category_ids } }
```

# Screenshots
<img width="658" alt="Screenshot 2024-04-08 at 2 39 22 PM" src="https://github.com/discourse/discourse-adplugin/assets/50783505/b44b386d-65a1-4a2a-a487-d735b13357dd">

# Preview Video

https://github.com/discourse/discourse-adplugin/assets/50783505/6d0d8253-afef-4e15-b6fc-c6f696efd169

assets/javascripts/discourse/components/house-ad.js

@@ -78,7 +78,14 @@ export default AdComponent.extend({
       }
       let ad = houseAds.creatives[adNames[adIndex[placement]]] || "";
       adIndex[placement] = (adIndex[placement] + 1) % adNames.length;
-      return ad;
+      // check if the ad includes the current category, or if no category restrictions are set for the ad
+      // otherwise don't show it
+      if (
+        !ad.category_ids?.length ||
+        ad.category_ids.includes(this.currentCategoryId)
+      ) {
+        return ad.html;
+      }
     } else {
       return "";
     }