Add regex validator to build order reference field

InvenTree/build/migrations/0019_auto_20201019_1302.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.0.7 on 2020-10-19 13:02
+
+import InvenTree.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('build', '0018_build_reference'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='build',
+            options={'verbose_name': 'Build Order', 'verbose_name_plural': 'Build Orders'},
+        ),
+        migrations.AlterField(
+            model_name='build',
+            name='reference',
+            field=models.CharField(help_text='Build Order Reference', max_length=64, unique=True, validators=[InvenTree.validators.validate_build_order_reference], verbose_name='Reference'),
+        ),
+    ]