It is done!

EllieHub/Common/AppConstants.cs

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+namespace EllieHub.Common;
+
+/// <summary>
+/// Defines the constants used throughout the whole application.
+/// </summary>
+public static class AppConstants 
+{
+    /// <summary>
+    /// Defines the location of the default image for the bot avatar.
+    /// </summary>
+    public const string BotAvatarUri = "avares://EllieHub/Assets/ellie.png";
+
+    /// <summary>
+    /// The name for an <see cref="HttpClient"/> that does not automatically follow redirect responses.
+    /// </summary>
+    public const string NoRedirectClient = "NoRedirect";
+}