Store what messages are read

Signed-off-by: Emmy D'Anello <emmy.danello@animath.fr>

chat/migrations/0003_message_users_read.py

@@ -0,0 +1,26 @@
+# Generated by Django 5.0.3 on 2024-04-28 18:52
+
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("chat", "0002_alter_channel_options_channel_category"),
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="message",
+            name="users_read",
+            field=models.ManyToManyField(
+                blank=True,
+                help_text="Users who have read the message.",
+                related_name="+",
+                to=settings.AUTH_USER_MODEL,
+                verbose_name="users read",
+            ),
+        ),
+    ]