Refs #28643 -- Added MD5 database function.

Thanks Tim Graham, Nick Pope and Simon Charette for reviews.

tests/db_functions/text/test_md5.py

@@ -0,0 +1,41 @@
+from django.db import connection
+from django.db.models import CharField
+from django.db.models.functions import MD5
+from django.test import TestCase
+from django.test.utils import register_lookup
+
+from ..models import Author
+
+
+class MD5Tests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        Author.objects.bulk_create([
+            Author(alias='John Smith'),
+            Author(alias='Jordan Élena'),
+            Author(alias='皇帝'),
+            Author(alias=''),
+            Author(alias=None),
+        ])
+
+    def test_basic(self):
+        authors = Author.objects.annotate(
+            md5_alias=MD5('alias'),
+        ).values_list('md5_alias', flat=True).order_by('pk')
+        self.assertSequenceEqual(
+            authors,
+            [
+                '6117323d2cabbc17d44c2b44587f682c',
+                'ca6d48f6772000141e66591aee49d56c',
+                'bf2c13bc1154e3d2e7df848cbc8be73d',
+                'd41d8cd98f00b204e9800998ecf8427e',
+                'd41d8cd98f00b204e9800998ecf8427e' if connection.features.interprets_empty_strings_as_nulls else None,
+            ],
+        )
+
+    def test_transform(self):
+        with register_lookup(CharField, MD5):
+            authors = Author.objects.filter(
+                alias__md5='6117323d2cabbc17d44c2b44587f682c',
+            ).values_list('alias', flat=True)
+            self.assertSequenceEqual(authors, ['John Smith'])