Added mailboxes as local data sources (#1022)

app/MindWork AI Studio/Settings/IDataSourceBase.cs

@@ -0,0 +1,21 @@
+using AIStudio.Settings.DataModel;
+using AIStudio.Tools.PluginSystem;
+
+namespace AIStudio.Settings;
+
+/// <summary>
+/// What every configured data source has, whichever list of the settings it is stored in.
+/// </summary>
+/// <remarks>
+/// Not every data source is an IDataSource. Those are the ones in DataSources, which classic RAG,
+/// Semantic Search and the agents read. A data source kept in a list of its own is never handed to
+/// them, and the compiler sees to that, because it implements only this interface or
+/// IIndexedDataSource.
+/// </remarks>
+public interface IDataSourceBase : IConfigurationObject
+{
+    /// <summary>
+    /// Which type of data source is this?
+    /// </summary>
+    public DataSourceType Type { get; init; }
+}