✨(backend) add email notifications for screen recordings

Implement backend method to send email notifications when screen recordings
are ready for download. Enables users to be alerted when their recordings are
available. Frontend implementation to follow in upcoming commits.

This service is triggered by the storage hook from Minio.

Add minimal unit test coverage for notification service, addressing previous
lack of tests in this area. The notification service was responsible for
calling the unstable summary service feature, which was developped way too
quickly.

The email template has been reviewed by a LLM, to make it user-friendly and
crystal clear.

src/backend/core/recording/event/notification.py

@@ -1,8 +1,13 @@
 """Service to notify external services when a new recording is ready."""
 
 import logging
+import smtplib
 
 from django.conf import settings
+from django.core.mail import send_mail
+from django.template.loader import render_to_string
+from django.utils.translation import get_language, override
+from django.utils.translation import gettext_lazy as _
 
 import requests
 
@@ -21,10 +26,7 @@ class NotificationService:
             return self._notify_summary_service(recording)
 
         if recording.mode == models.RecordingModeChoices.SCREEN_RECORDING:
-            logger.warning(
-                "Screen recording mode not implemented for recording %s", recording.id
-            )
-            return False
+            return self._notify_user_by_email(recording)
 
         logger.error(
             "Unknown recording mode %s for recording %s",
@@ -33,6 +35,59 @@ class NotificationService:
         )
         return False
 
+    @staticmethod
+    def _notify_user_by_email(recording) -> bool:
+        """
+        Send an email notification to recording owners when their recording is ready.
+
+        The email includes a direct link that redirects owners to a dedicated download
+        page in the frontend where they can access their specific recording.
+        """
+
+        owner_accesses = models.RecordingAccess.objects.select_related("user").filter(
+            role=models.RoleChoices.OWNER,
+            recording_id=recording.id,
+        )
+
+        if not owner_accesses:
+            logger.error("No owner found for recording %s", recording.id)
+            return False
+
+        language = get_language()
+
+        context = {
+            "brandname": settings.EMAIL_BRAND_NAME,
+            "support_email": settings.EMAIL_SUPPORT_EMAIL,
+            "logo_img": settings.EMAIL_LOGO_IMG,
+            "domain": settings.EMAIL_DOMAIN,
+            "room_name": recording.room.name,
+            "recording_date": recording.created_at.strftime("%A %d %B %Y"),
+            "recording_time": recording.created_at.strftime("%H:%M"),
+            "link": f"{settings.SCREEN_RECORDING_BASE_URL}/{recording.id}",
+        }
+
+        emails = [access.user.email for access in owner_accesses]
+
+        with override(language):
+            msg_html = render_to_string("mail/html/screen_recording.html", context)
+            msg_plain = render_to_string("mail/text/screen_recording.txt", context)
+            subject = str(_("Your recording is ready"))  # Force translation
+
+            try:
+                send_mail(
+                    subject.capitalize(),
+                    msg_plain,
+                    settings.EMAIL_FROM,
+                    emails,
+                    html_message=msg_html,
+                    fail_silently=False,
+                )
+            except smtplib.SMTPException as exception:
+                logger.error("notification to %s was not sent: %s", emails, exception)
+                return False
+
+        return True
+
     @staticmethod
     def _notify_summary_service(recording):
         """Notify summary service about a new recording."""