Added mailboxes as local data sources (#1022)

app/MindWork AI Studio/Tools/Mail/MailText.cs

@@ -0,0 +1,19 @@
+namespace AIStudio.Tools.Mail;
+
+/// <summary>
+/// One mail as text, the way AI Studio indexes it and a model gets to read it.
+/// </summary>
+/// <param name="HeaderBlock">The lines written above the text: who wrote to whom, when, and about what.</param>
+/// <param name="Body">The text of the mail, empty when it is encrypted or has none.</param>
+/// <param name="Subject">The subject on one line, empty when the mail has none.</param>
+/// <param name="EncryptionKind">How the content is encrypted, NONE when it is readable.</param>
+/// <param name="Importance">How important the sender marked the mail.</param>
+/// <param name="BodySource">Which part of the mail the text was read from.</param>
+public sealed record MailText(string HeaderBlock, string Body, string Subject, MailEncryptionKind EncryptionKind, MailImportance Importance, MailBodySource BodySource)
+{
+    /// <summary>
+    /// The header block and the text together, which is what gets cut into chunks: the first
+    /// chunk starts with the header block, so a search for a sender or a subject finds the mail.
+    /// </summary>
+    public string FullText => this.Body.Length is 0 ? this.HeaderBlock : $"{this.HeaderBlock}\n\n{this.Body}";
+}