Added a home page prompt for missing API keys of enterprise providers (#1056)

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

app/MindWork AI Studio/Tools/UserAPIKeys/PendingUserAPIKeyTarget.cs

@@ -0,0 +1,12 @@
+using AIStudio.Provider;
+
+namespace AIStudio.Tools.UserAPIKeys;
+
+/// <summary>
+/// One provider of a configuration plugin which waits for the API key of the user.
+/// </summary>
+/// <param name="Name">The name of the provider as the user knows it.</param>
+/// <param name="SecretId">Where the API key of the provider is stored.</param>
+/// <param name="StoreType">The secret store of the provider's kind, which also tells which models the provider offers.</param>
+/// <param name="CreateProvider">Creates the provider, e.g., to check a key. Called only on demand, since every provider brings an HTTP client of its own.</param>
+public sealed record PendingUserAPIKeyTarget(string Name, ISecretId SecretId, SecretStoreType StoreType, Func<IProvider> CreateProvider);