Added mailboxes as local data sources (#1022)

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

@@ -0,0 +1,22 @@
+namespace AIStudio.Tools.Mail;
+
+/// <summary>
+/// What a provider expects as the username for its IMAP server.
+/// </summary>
+public enum MailboxUsernameFormat
+{
+    /// <summary>
+    /// The full e-mail address.
+    /// </summary>
+    EMAIL_ADDRESS,
+
+    /// <summary>
+    /// The part of the e-mail address before the @ sign, e.g., at iCloud.
+    /// </summary>
+    ADDRESS_NAME_PART,
+
+    /// <summary>
+    /// The account in the directory of the organization, e.g., at an Exchange server.
+    /// </summary>
+    DOMAIN_ACCOUNT,
+}