💩(backend) notify the summary service when a new recording is available

Draft a piece of code to try the feature in staging. I'll consolidate this
implementation ASAP, as soon we have a first implementation functional.

What's missing?
- when owners are multiple
- retry when the backend cannot reach the summary service
- factorize the key oneliner, duplicated from the egress service
- optimize SQL query
- unit tests

src/backend/core/migrations/0009_alter_recording_status.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.1.3 on 2024-12-02 13:23
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0008_user_full_name_user_short_name'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='recording',
+            name='status',
+            field=models.CharField(choices=[('initiated', 'Initiated'), ('active', 'Active'), ('stopped', 'Stopped'), ('saved', 'Saved'), ('aborted', 'Aborted'), ('failed_to_start', 'Failed to Start'), ('failed_to_stop', 'Failed to Stop'), ('notification_succeeded', 'Notification succeeded')], default='initiated', max_length=50),
+        ),
+    ]