Fixed #18468 -- Added support for comments on columns and tables.

Thanks Jared Chung, Tom Carrick, David Smith, Nick Pope, and Mariusz
Felisiak for reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Nick Pope <nick@nickpope.me.uk>

tests/invalid_models_tests/test_models.py

@@ -1872,6 +1872,37 @@ class OtherModelTests(SimpleTestCase):
         )
 
 
+@isolate_apps("invalid_models_tests")
+class DbTableCommentTests(TestCase):
+    def test_db_table_comment(self):
+        class Model(models.Model):
+            class Meta:
+                db_table_comment = "Table comment"
+
+        errors = Model.check(databases=self.databases)
+        expected = (
+            []
+            if connection.features.supports_comments
+            else [
+                Warning(
+                    f"{connection.display_name} does not support comments on tables "
+                    f"(db_table_comment).",
+                    obj=Model,
+                    id="models.W046",
+                ),
+            ]
+        )
+        self.assertEqual(errors, expected)
+
+    def test_db_table_comment_required_db_features(self):
+        class Model(models.Model):
+            class Meta:
+                db_table_comment = "Table comment"
+                required_db_features = {"supports_comments"}
+
+        self.assertEqual(Model.check(databases=self.databases), [])
+
+
 class MultipleAutoFieldsTests(TestCase):
     def test_multiple_autofields(self):
         msg = (