Added backups of all data, restorable on another computer (#1008)

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

app/Tests/Tools/FirstPluginLoadTests.cs

@@ -0,0 +1,50 @@
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks that indexing waits for the plugins before its first run, but never for good.
+/// </summary>
+/// <remarks>
+/// The embedding providers of an organization come with its configuration plugin. Right after a
+/// backup was restored, the settings do not hold them yet, and a first run which starts before the
+/// plugins were loaded finds the data sources of the user without their embedding provider. Should
+/// loading fail, though, waiting for it must not keep every data source from being indexed.
+/// </remarks>
+[TestFixture]
+public sealed class FirstPluginLoadTests
+{
+    [Test]
+    public async Task TheFirstRunWaitsUntilThePluginsWereLoaded()
+    {
+        var firstLoad = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var wait = DataSourceEmbeddingService.WaitForFirstPluginLoadAsync(firstLoad.Task, TimeSpan.FromMinutes(1), CancellationToken.None);
+
+        await Task.Delay(50);
+        Assert.That(wait.IsCompleted, Is.False, "The plugins are still loading.");
+
+        firstLoad.SetResult();
+        Assert.That(await wait, Is.True);
+    }
+
+    [Test]
+    public async Task TheFirstRunStartsAnywayWhenLoadingThePluginsTakesTooLong()
+    {
+        var neverLoaded = new TaskCompletionSource();
+
+        var loadedInTime = await DataSourceEmbeddingService.WaitForFirstPluginLoadAsync(neverLoaded.Task, TimeSpan.FromMilliseconds(50), CancellationToken.None);
+
+        Assert.That(loadedInTime, Is.False, "Loading may fail for good, and the data sources must be indexed all the same.");
+    }
+
+    [Test]
+    public void StoppingAIStudioEndsTheWait()
+    {
+        var neverLoaded = new TaskCompletionSource();
+        using var stopping = new CancellationTokenSource();
+        stopping.Cancel();
+
+        var waiting = DataSourceEmbeddingService.WaitForFirstPluginLoadAsync(neverLoaded.Task, TimeSpan.FromMinutes(1), stopping.Token);
+        Assert.That(async () => await waiting, Throws.InstanceOf<OperationCanceledException>());
+    }
+}