Added mailboxes as local data sources (#1022)

app/MindWork AI Studio/Tools/ExternalHttpClientTimeout.cs

@@ -60,6 +60,27 @@ public static class ExternalHttpClientTimeout
             ValidateServerCertificateWithCustomRootCertificates(host, certificate, chain, sslPolicyErrors, customRootCertificateCache, trustPolicy);
     }
 
+    /// <summary>
+    /// The certificate validation for a TLS connection which does not go through HTTP, e.g., to an IMAP server.
+    /// </summary>
+    /// <remarks>
+    /// The same rules apply as to HTTPS: the system trust first, and the configured root certificates
+    /// only for the allowed hosts. This matters most in a Flatpak, which does not see the root
+    /// certificates of the OS, so that a server with an internal CA fails without the bundle.
+    /// </remarks>
+    /// <param name="host">The host the connection goes to, as an IDN host.</param>
+    /// <param name="trustPolicy">Whether the configured root certificates may be used.</param>
+    /// <returns>The callback, or null when no configured root certificates are usable and the system trust decides alone.</returns>
+    public static RemoteCertificateValidationCallback? CreateServerCertificateValidationCallback(string host, ExternalHttpTrustPolicy trustPolicy)
+    {
+        var customRootCertificateCache = GetCustomRootCertificateCache();
+        if (!customRootCertificateCache.State.IsUsable)
+            return null;
+
+        return (_, certificate, chain, sslPolicyErrors) =>
+            ValidateServerCertificateWithCustomRootCertificates(host, certificate, chain, sslPolicyErrors, customRootCertificateCache, trustPolicy);
+    }
+
     public static ExternalHttpCustomRootCertificateState CustomRootCertificateState => GetCustomRootCertificateCache().State;
 
     public static string GetTimeoutDescription()
@@ -500,7 +521,6 @@ public static class ExternalHttpClientTimeout
     {
         var chainStatuses = FormatChainStatusesForLog(chain.ChainStatus);
         var elementStatuses = chain.ChainElements
-            .Cast<X509ChainElement>()
             .Select((element, index) => $"element {index}: {FormatChainStatusesForLog(element.ChainElementStatus)}")
             .ToList();
         LOGGER.Value.LogError($"Rejected external HTTPS certificate for '{HostForLog(host)}' after validation with configured custom root certificates. TLS policy errors: {sslPolicyErrors}. Chain statuses: {chainStatuses}. Chain element statuses: {string.Join("; ", elementStatuses)}");