Added user-managed API keys for enterprise-configured providers (#919)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/PluginSystem/IUserProvidedAPIKey.cs

@@ -0,0 +1,15 @@
+namespace AIStudio.Tools.PluginSystem;
+
+/// <summary>
+/// Represents a configuration object whose API key is managed by the user, although the object
+/// itself is managed by a configuration plugin. Implemented by all provider kinds which support
+/// the "AllowUserProvidedAPIKey" option, i.e., LLM, embedding, and transcription providers.
+/// </summary>
+public interface IUserProvidedAPIKey
+{
+    /// <summary>
+    /// When set by a configuration plugin, the user may set their own API key for this otherwise
+    /// locked, enterprise-managed object.
+    /// </summary>
+    public bool AllowUserProvidedAPIKey { get; }
+}