Adds a "filename_template" field to reports

- Allows users to define the naming scheme for generated reports
- Templated, can use any context variable already available to the report instance
- Adds some more context variables to various reports

InvenTree/report/migrations/0016_auto_20210513_1303.py

@@ -0,0 +1,38 @@
+# Generated by Django 3.2 on 2021-05-13 03:03
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('report', '0015_auto_20210403_1837'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='billofmaterialsreport',
+            name='filename_pattern',
+            field=models.CharField(default='report.pdf', help_text='Pattern for generating report filenames', max_length=100, verbose_name='Filename Pattern'),
+        ),
+        migrations.AddField(
+            model_name='buildreport',
+            name='filename_pattern',
+            field=models.CharField(default='report.pdf', help_text='Pattern for generating report filenames', max_length=100, verbose_name='Filename Pattern'),
+        ),
+        migrations.AddField(
+            model_name='purchaseorderreport',
+            name='filename_pattern',
+            field=models.CharField(default='report.pdf', help_text='Pattern for generating report filenames', max_length=100, verbose_name='Filename Pattern'),
+        ),
+        migrations.AddField(
+            model_name='salesorderreport',
+            name='filename_pattern',
+            field=models.CharField(default='report.pdf', help_text='Pattern for generating report filenames', max_length=100, verbose_name='Filename Pattern'),
+        ),
+        migrations.AddField(
+            model_name='testreport',
+            name='filename_pattern',
+            field=models.CharField(default='report.pdf', help_text='Pattern for generating report filenames', max_length=100, verbose_name='Filename Pattern'),
+        ),
+    ]