Add link field to collection and fix the visited counter in collection page

backend/server/adventures/migrations/0010_collection_link.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.0.8 on 2024-10-08 03:05
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('adventures', '0009_alter_adventure_type'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='collection',
+            name='link',
+            field=models.URLField(blank=True, max_length=2083, null=True),
+        ),
+    ]