[Activity] Add CDN refresh

Cocotte/Utils/CdnUtils.cs

@@ -0,0 +1,19 @@
+namespace Cocotte.Utils;
+
+public class CdnUtils
+{
+    /// <summary>
+    /// Use this to force discord media cache to fetch new content from CDN
+    /// </summary>
+    private const string QuerySuffix = $"?q={RandomSuffix}";
+
+    /// <summary>
+    /// Needs to be updated each time a media is updated on the CDN
+    /// </summary>
+    private const string RandomSuffix = "a57z45a";
+
+    public static string GetAsset(string assetName)
+    {
+        return $"https://sage.cdn.ilysix.fr/assets/Cocotte/{assetName}{QuerySuffix}";
+    }
+}