Added mailboxes as local data sources (#1022)

app/Tests/Settings/MailboxMaxAgeTests.cs

@@ -0,0 +1,23 @@
+using AIStudio.Settings.DataModel;
+
+namespace AIStudio.Tests.Settings;
+
+/// <summary>
+/// Checks the first day of the period a mailbox is indexed for.
+/// </summary>
+[TestFixture]
+public sealed class MailboxMaxAgeTests
+{
+    private static readonly DateTimeOffset NOW = new(2026, 10, 2, 9, 30, 0, TimeSpan.FromHours(2));
+
+    [TestCase(MailboxMaxAge.LAST_3_MONTHS, 2026, 7)]
+    [TestCase(MailboxMaxAge.LAST_6_MONTHS, 2026, 4)]
+    [TestCase(MailboxMaxAge.LAST_12_MONTHS, 2025, 10)]
+    [TestCase(MailboxMaxAge.LAST_24_MONTHS, 2024, 10)]
+    [TestCase((MailboxMaxAge)42, 2026, 7)]
+    public void ThePeriodStartsMonthsBack(MailboxMaxAge maxAge, int year, int month) =>
+        Assert.That(maxAge.GetReceivedSince(NOW), Is.EqualTo(new DateTimeOffset(year, month, 2, 9, 30, 0, TimeSpan.FromHours(2))));
+
+    [Test]
+    public void AllMailsHaveNoFirstDay() => Assert.That(MailboxMaxAge.ALL.GetReceivedSince(NOW), Is.Null);
+}