Move apps in main directory

Signed-off-by: Emmy D'Anello <emmy.danello@animath.fr>

registration/api/views.py

@@ -0,0 +1,15 @@
+# Copyright (C) 2020 by Animath
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from django_filters.rest_framework import DjangoFilterBackend
+from rest_framework.viewsets import ModelViewSet
+
+from .serializers import RegistrationSerializer
+from ..models import Registration
+
+
+class RegistrationViewSet(ModelViewSet):
+    queryset = Registration.objects.all()
+    serializer_class = RegistrationSerializer
+    filter_backends = [DjangoFilterBackend]
+    filterset_fields = ['user', 'participantregistration__team', ]