CeleryApp allows overriding the task class. (#78)

* CeleryApp allows overriding the task class.

Fixes #76

* Don't set test app as current

tenant_schemas_celery/app.py

@@ -76,10 +76,11 @@ def restore_schema(task, **kwargs):
 
 class CeleryApp(Celery):
     registry_cls = 'tenant_schemas_celery.registry:TenantTaskRegistry'
-
+    task_cls = 'tenant_schemas_celery.task:TenantTask'
+
     def create_task_cls(self):
         return self.subclass_with_self(
-            "tenant_schemas_celery.task:TenantTask",
+            self.task_cls,
             abstract=True,
             name="TenantTask",
             attribute="_app",

tenant_schemas_celery/app_test.py

@@ -0,0 +1,32 @@
+from tenant_schemas_celery.app import CeleryApp
+from tenant_schemas_celery.task import TenantTask
+
+
+class DummyTask(TenantTask):
+    ...
+
+
+def test_celery_app_should_allow_overriding_task_cls_as_object() -> None:
+    class App(CeleryApp):
+        task_cls = DummyTask
+
+    app = App(set_as_current=False)
+
+    @app.task()
+    def some_task() -> None:
+        ...
+
+    assert isinstance(some_task, DummyTask)
+
+
+def test_celery_app_should_allow_overriding_task_cls_as_string() -> None:
+    class App(CeleryApp):
+        task_cls = f"{DummyTask.__module__}:{DummyTask.__name__}"
+
+    app = App(set_as_current=False)
+
+    @app.task()
+    def some_task() -> None:
+        ...
+
+    assert isinstance(some_task, DummyTask)