Implement support for sets and other improvements (#34)

* Add a boolean to define item as part of a set
* Add contextual help in admin
* Introduce support to sets and to item code lookup
Also review the url path for pagination

ram/roster/migrations/0025_rollingstock_set_alter_rollingstock_era_and_more.py

@@ -0,0 +1,40 @@
+# Generated by Django 5.0.4 on 2024-04-20 12:55
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("roster", "0024_rollingstock_description"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="rollingstock",
+            name="set",
+            field=models.BooleanField(default=False, help_text="Part of a set"),
+        ),
+        migrations.AlterField(
+            model_name="rollingstock",
+            name="era",
+            field=models.CharField(
+                blank=True, help_text="Era or epoch of the model", max_length=32
+            ),
+        ),
+        migrations.AlterField(
+            model_name="rollingstock",
+            name="item_number",
+            field=models.CharField(
+                blank=True, help_text="Catalog item number or code", max_length=32
+            ),
+        ),
+        migrations.AlterField(
+            model_name="rollingstockjournal",
+            name="private",
+            field=models.BooleanField(
+                default=False,
+                help_text="Journal log will be visible only to logged users",
+            ),
+        ),
+    ]