Show warning message when there are many/stale snappea tasks

As discussed in #11, there are scenarios (e.g. misconfiguration) where snappea
does not pick up the tasks. Events not showing up in Bugsink, w/o further
indication why that may be, leaves people confused. Better to warn explicitly
in that case.

snappea/migrations/0003_task_created_at.py

@@ -0,0 +1,22 @@
+# Generated by Django 4.2.16 on 2024-11-15 10:42
+
+from django.db import migrations, models
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("snappea", "0002_create_models"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="task",
+            name="created_at",
+            field=models.DateTimeField(
+                auto_now_add=True, default=django.utils.timezone.now
+            ),
+            preserve_default=False,
+        ),
+    ]

snappea/models.py

@@ -7,6 +7,7 @@ from . import thread_uuid
 
 
 class Task(models.Model):
+    created_at = models.DateTimeField(auto_now_add=True)
     task_name = models.CharField(max_length=255)
     args = models.TextField(null=False, default='[]')
     kwargs = models.TextField(null=False, default='{}')