Fixed #34112 -- Added async-compatible interface to Model methods.

Thanks Adam Johnson for the review.

tests/async/test_async_model_methods.py

@@ -0,0 +1,25 @@
+from django.test import TestCase
+
+from .models import SimpleModel
+
+
+class AsyncModelOperationTest(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.s1 = SimpleModel.objects.create(field=0)
+
+    async def test_asave(self):
+        self.s1.field = 10
+        await self.s1.asave()
+        refetched = await SimpleModel.objects.aget()
+        self.assertEqual(refetched.field, 10)
+
+    async def test_adelete(self):
+        await self.s1.adelete()
+        count = await SimpleModel.objects.acount()
+        self.assertEqual(count, 0)
+
+    async def test_arefresh_from_db(self):
+        await SimpleModel.objects.filter(pk=self.s1.pk).aupdate(field=20)
+        await self.s1.arefresh_from_db()
+        self.assertEqual(self.s1.field, 20)