feat(rdfimport): add get_or_create method to models

Add `get_or_create_uri` methods to models to create new
objects from RDF data if the URIs in question don't already
exist.

apis_ontology/models.py

@@ -1,5 +1,6 @@
 from apis_core.apis_entities.models import AbstractEntity
 from apis_core.apis_relations.models import Property
+from apis_core.utils.helpers import create_object_from_uri
 from dateparser import parse
 from django.conf import settings
 from django.contrib.contenttypes.models import ContentType
@@ -766,6 +767,10 @@ class Person(PersonNameMixin, DescriptionMixin, StatusMixin, AbstractEntity):
     class Meta:
         verbose_name_plural = _("personen")
 
+    @classmethod
+    def get_or_create_uri(cls, uri):
+        return create_object_from_uri(uri, cls) or cls.objects.get(pk=uri)
+
 
 class Organisation(
     GenericNameMixin,
@@ -915,6 +920,10 @@ class Meta:
         verbose_name = _("ort")
         verbose_name_plural = _("orte")
 
+    @classmethod
+    def get_or_create_uri(cls, uri):
+        return create_object_from_uri(uri, cls) or cls.objects.get(pk=uri)
+
 
 class ResearchPerspective(
     GenericNameMixin,