Add migration test files for drop table issue

Author: absci

testapp/migrations/0008_test_drop_table_with_foreign_key_reference_part1.py

@@ -0,0 +1,22 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('testapp', '0007_test_remove_onetoone_field_part2'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="Pony",
+            fields=[
+                ("id", models.AutoField(primary_key=True)),
+            ]),
+        migrations.CreateModel(
+            name="Rider",
+            fields=[
+                ("id", models.AutoField(primary_key=True)),
+                ("pony", models.ForeignKey("testapp.Pony", models.CASCADE)),
+            ]),
+    ]

testapp/migrations/0009_test_drop_table_with_foreign_key_reference_part2.py

@@ -0,0 +1,16 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    '''
+    Sql server will generate a error if drop a table that is referenced by a foreign key constraint.
+    This test is to check if the table can be dropped correctly. 
+    '''
+    dependencies = [
+        ('testapp', '0008_test_drop_table_with_foreign_key_reference_part1'),
+    ]
+
+    operations = [
+        migrations.DeleteModel("Pony"),
+        migrations.DeleteModel("Rider"),
+    ]