Fixing the composing docs that i messed up

Implementation/Composing/index-v9.md

@@ -61,6 +61,75 @@ namespace My.Website
     }
 }
 
+```
+
+:::warning
+Ordering of composers is important, the last one added can override a previously added composer! Make sure, when overriding,
+that your composer that is doing the overriding, is 'composing', after the composer has 'composed' the element you wish to override!
+:::
+
+### Example - Explicitly Registering a new custom OEmbedProvider
+This example shows a custom 'Spotify' OEmbed Provider which will allow Spotify URLs to be used via the 'embed' button in the Grid and Rich Text Editors. As the collection for OEmbedProviders is not 'typed scanned', we need to explicitly register the provider in the collection of OEmbedProviders. We create a C# class which implements `IUserComposer` and append our new Spotify OEmbedProvider to the OEmbedProviders() collection:
+
+```csharp
+using System.Collections.Generic;
+using Umbraco.Cms.Core.Media.EmbedProviders;
+using Umbraco.Cms.Core.Serialization;
+namespace My.Website
+{
+    public class Spotify : EmbedProviderBase
+    {
+        public Spotify(IJsonSerializer jsonSerializer)
+            : base(jsonSerializer)
+        {
+        }
+        public override string ApiEndpoint => "https://embed.spotify.com/oembed/";
+        // Playlist
+        // https://open.spotify.com/user/spotify/playlist/37i9dQZF1E4sNI4jZloSZr?si=cueBooBfTnqCGriSa4N_Kg
+        // spotify:user:spotify:playlist:37i9dQZF1E4sNI4jZloSZr
+        // Artist
+        // https://open.spotify.com/artist/0iirUbtgwt9jEkc2Grin8C?si=TLeUR2cHR-KPRJJhW6YiVg
+        // spotify:artist:0iirUbtgwt9jEkc2Grin8C
+        // Album
+        // https://open.spotify.com/album/0lvtdqkqIln6uDBBUT7DHL?si=XTVJIEmnS_OVv9l6ktPFiw
+        // spotify:album:0lvtdqkqIln6uDBBUT7DHL
+        // Track
+        // https://open.spotify.com/track/7aCk4XfXIEJM2MecU6Gmf2?si=vESDzI0xTNeA9FQ_dvf1eQ
+        // spotify:track:7aCk4XfXIEJM2MecU6Gmf2
+        public override string[] UrlSchemeRegex => new string[]
+        {
+            @".*.spotify.com/.*",
+            @"spotify:.*"
+        };
+        public override Dictionary<string, string> RequestParams => new Dictionary<string, string>();
+        public override string GetMarkup(string url, int maxWidth = 0, int maxHeight = 0)
+        {
+            var requestUrl = base.GetEmbedProviderUrl(url, maxWidth, maxHeight);
+            var oembed = base.GetJsonResponse<OEmbedResponse>(requestUrl);
+            return oembed.GetHtml();
+        }
+    }
+}
+```
+
+```csharp
+using Umbraco.Cms.Core.Composing;
+using Umbraco.Cms.Core.DependencyInjection;
+namespace My.Website
+{
+    public class CustomOEmbedComposer : IComposer
+    {
+        public void Compose(IUmbracoBuilder builder)
+        {
+            // Change the OEmbedProviders collection
+            // by adding our new EmbedProvider for Spotify
+            builder.OEmbedProviders().Append<Spotify>();
+        }
+    }
+}
+```
+See a list of collections below to determine which are 'type scanned' and which require explicit registration.
+
 ### ComponentComposer&lt;T&gt;
 It's an implementation of `IComposer`, that provides a quicker way to add a custom component to the Component's collection. Creating a C# class that inherits from `ComponentComposer<YourComponentType>` will automatically add `YourComponentType` to the collection of Components. In the example above, the `SubscribeToContentServiceSavingComposer` for the `SubscribeToContentServiceSavingComponent` could have been written more conveniently as: