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/consist/migrations/0011_alter_consist_consist_address_alter_consist_era.py

@@ -0,0 +1,30 @@
+# Generated by Django 5.0.4 on 2024-04-20 12:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("consist", "0010_alter_consist_notes"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="consist",
+            name="consist_address",
+            field=models.SmallIntegerField(
+                blank=True,
+                default=None,
+                help_text="DCC consist address if enabled",
+                null=True,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="consist",
+            name="era",
+            field=models.CharField(
+                blank=True, help_text="Era or epoch of the consist", max_length=32
+            ),
+        ),
+    ]