Fix HealthCheckView.as_view() returning None (#598)

`HealthCheckView.as_view()` returns `None` instead of a callable view
function, causing `TypeError` when passed to Django's `path()`.


---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: codingjoe <1772890+codingjoe@users.noreply.github.com>

Author: Copilot

health_check/views.py

@@ -161,7 +161,7 @@ def as_view(cls, **initkwargs):
                 DeprecationWarning,
                 stacklevel=2,
             )
-        super().as_view(**initkwargs)
+        return super().as_view(**initkwargs)
 
     def get_plugins(self):
         for check in self.checks or [

tests/test_views.py

@@ -10,7 +10,7 @@
 from health_check.conf import HEALTH_CHECK
 from health_check.exceptions import ServiceWarning
 from health_check.plugins import plugin_dir
-from health_check.views import MediaType
+from health_check.views import HealthCheckView, MediaType
 
 
 class TestMediaType:
@@ -326,3 +326,22 @@ def test_non_native_atomic_request(self, settings, monkeypatch, client):
         response = client.get(self.url)
         assert response.status_code == 500
         assert b"System status" in response.content
+
+
+class TestHealthCheckView:
+    def test_as_view__return_callable(self):
+        """Return a callable view function."""
+        view = HealthCheckView.as_view()
+        assert callable(view)
+
+    def test_as_view__warn_warnings_as_errors(self):
+        """Emit deprecation warning when warnings_as_errors is passed."""
+        with pytest.warns(DeprecationWarning, match=r"`warnings_as_errors` argument is deprecated"):
+            view = HealthCheckView.as_view(warnings_as_errors=True)
+        assert callable(view)
+
+    def test_as_view__warn_use_threading(self):
+        """Emit deprecation warning when use_threading is passed."""
+        with pytest.warns(DeprecationWarning, match=r"`use_threading` argument is deprecated"):
+            view = HealthCheckView.as_view(use_threading=True)
+        assert callable(view)