fix(notifications): EWS sender review follow-ups — https guard, transient-path logging, test hardening

src/ZB.MOM.WW.ScadaBridge.NotificationService/Ews/EwsSoapMailSender.cs

@@ -68,6 +68,19 @@ public sealed class EwsSoapMailSender : IEwsMailSender
     {
         ArgumentNullException.ThrowIfNull(request);
 
+        // Defense in depth: a Basic header is a replayable cleartext credential, so it never
+        // leaves this process over anything but https — not even if a misconfigured
+        // SmtpConfiguration row supplies an http:// URL. Config defects do not improve on
+        // retry, so this is permanent. Only the scheme and host appear in the message.
+        if (!string.Equals(request.Endpoint.Scheme, Uri.UriSchemeHttps, StringComparison.OrdinalIgnoreCase))
+        {
+            var schemeError =
+                $"EWS endpoint '{request.Endpoint.Scheme}://{request.Endpoint.Host}' is not https; " +
+                "Basic credentials are only ever sent over https.";
+            _logger.LogError("Permanent EWS failure: {Detail}", schemeError);
+            throw new EwsPermanentException(schemeError);
+        }
+
         var envelope = EwsSoapEnvelope.BuildCreateItem(
             request.FromAddress, request.BccRecipients, request.Subject, request.Body);
 
@@ -114,7 +127,14 @@ public sealed class EwsSoapMailSender : IEwsMailSender
         }
         catch (Exception ex) when (ex is HttpRequestException or OperationCanceledException)
         {
-            // Transport failure or our own timeout — availability-shaped, so retry.
+            // Transport failure or our own timeout — availability-shaped, so retry. Logged with
+            // the host and exception type only: the exception message is untrusted text and the
+            // recipient addresses are notification content.
+            _logger.LogWarning(
+                "Transient EWS failure contacting {EwsHost} ({ExceptionType}).",
+                request.Endpoint.Host,
+                ex.GetType().Name);
+
             throw new EwsTransientException(
                 Scrub(
                     $"EWS request to {request.Endpoint.Host} failed: {ex.Message}",