Make generic models swappable

Suggestions from code review

Co-authored-by: Bruno Alla <[email protected]>

Author: diegocastrum

django_celery_results/models/generic.py

@@ -15,6 +15,7 @@ class Meta(AbstractTaskResult.Meta):
 
         abstract = False
         app_label = "django_celery_results"
+        swappable = "CELERY_RESULTS_TASKRESULT_MODEL"
 
 
 class ChordCounter(AbstractChordCounter):
@@ -25,6 +26,7 @@ class Meta(AbstractChordCounter.Meta):
 
         abstract = False
         app_label = "django_celery_results"
+        swappable = "CELERY_RESULTS_CHORDCOUNTER_MODEL"
 
 
 class GroupResult(AbstractGroupResult):
@@ -35,3 +37,4 @@ class Meta(AbstractGroupResult.Meta):
 
         abstract = False
         app_label = "django_celery_results"
+        swappable = "CELERY_RESULTS_GROUPRESULT_MODEL"