Add QuerySet.first_or_none (#1137)

* Add QuerySet.first_or_none

* restore docstrings for exceptions

---------

Co-authored-by: collerek <collerek@gmail.com>

tests/test_model_definition/test_models.py

@@ -451,6 +451,11 @@ async def test_offset():
 async def test_model_first():
     async with base_ormar_config.database:
         async with base_ormar_config.database.transaction(force_rollback=True):
+            with pytest.raises(ormar.NoMatch):
+                await User.objects.first()
+
+            assert await User.objects.first_or_none() is None
+
             tom = await User.objects.create(name="Tom")
             jane = await User.objects.create(name="Jane")
 
@@ -460,6 +465,9 @@ async def test_model_first():
             with pytest.raises(NoMatch):
                 await User.objects.filter(name="Lucy").first()
 
+            assert await User.objects.first_or_none(name="Lucy") is None
+            assert await User.objects.filter(name="Lucy").first_or_none() is None
+
             assert await User.objects.order_by("name").first() == jane