feat: implement dumpdata view

This view provides a way to serialize the whole database using json -
getting a fixture with natural foreign keys. This fixture lets us
reimport the database in a new installation.

Closes: #273

apis_core/core/views.py

@@ -0,0 +1,73 @@
+from django.http import HttpResponse
+from django.views import View
+from django.contrib.auth.mixins import UserPassesTestMixin
+
+from django.apps import apps
+from django.core import serializers
+from django.db import DEFAULT_DB_ALIAS, router
+
+from apis_core.apis_entities.models import AbstractEntity
+
+
+class Dumpdata(UserPassesTestMixin, View):
+    """
+    This view is loosely based on the `dumpdata` admin command.
+    It iterates throug the relevant app models and exports them using
+    the json serializer and natural foreign keys.
+    This way we can reimport this into a newly created Django APIS app
+    """
+
+    def test_func(self):
+        return self.request.user.is_staff
+
+    def get_objects(self, models, *args, **kwargs):
+        for model in models:
+            if not model._meta.proxy and router.allow_migrate_model(
+                DEFAULT_DB_ALIAS, model
+            ):
+                objects = model._default_manager
+                queryset = objects.using(DEFAULT_DB_ALIAS).order_by(model._meta.pk.name)
+                yield from queryset.iterator()
+
+    def get(self, request, *args, **kwargs):
+        # get all APIS apps and all APIS models
+        apis_app_labels = ["apis_relations", "apis_metainfo"]
+        apis_app_models = [
+            model
+            for model in apps.get_models()
+            if model._meta.app_label in apis_app_labels
+        ]
+
+        # create a list of app labels we want to iterate
+        # this allows to extend the apps via the ?app_labels= parameter
+        app_labels = set(apis_app_labels)
+        app_labels |= set(request.GET.get("app_labels", []))
+
+        # look for models that inherit from APIS models and add their
+        # app label to app_labels
+        for model in apps.get_models():
+            if any(map(lambda x: issubclass(model, x), apis_app_models)):
+                app_labels.add(model._meta.app_label)
+
+        # now go through all app labels
+        app_list = {}
+        for app_label in app_labels:
+            app_config = apps.get_app_config(app_label)
+            app_list[app_config] = None
+
+        models = serializers.sort_dependencies(app_list.items(), allow_cycles=True)
+
+        headers = {
+            "Content-Type": "application/json",
+        }
+        hr = HttpResponse(headers=headers)
+
+        serializers.serialize(
+            "json",
+            self.get_objects(models),
+            indent=2,
+            use_natural_foreign_keys=True,
+            stream=hr,
+        )
+
+        return hr

apis_core/urls.py

@@ -101,6 +101,8 @@ def build_apis_mock_request(method, path, view, original_request, **kwargs):
     return request
 
 
+from apis_core.core.views import Dumpdata
+
 urlpatterns = [
     path("", TemplateView.as_view(template_name="base.html"), name="apis_index"),
     path("admin/", admin.site.urls),
@@ -160,6 +162,7 @@ def build_apis_mock_request(method, path, view, original_request, **kwargs):
     ),
     # url(r'^docs/', include('sphinxdoc.urls')),
     # url(r'^accounts/', include('registration.backends.simple.urls')),
+    path("dumpdata.json", Dumpdata.as_view()),
 ]
 
 if "apis_fulltext_download" in settings.INSTALLED_APPS: