Refactor update creation api

This merge request does the following:

• Raise DRF errors rather than returning response to take advantage of the DRF exception handling mechanism
• Create serialisers for PUT request to simplify the code
• Improve validation checks in several places
• Fixes several issues in DRF infrastructure uses
• Fixes JSON fields handling
• Remove routes that do no fully qualify objects
• Implement a custom DRF exception handler that will allow to log errors
• Improve testing
• Improve permission management

beat/web/code/api.py

@@ -228,16 +228,7 @@ class RetrieveUpdateDestroyCodeView(RetrieveUpdateDestroyContributionView):
         return modified, db_object
 
     def get(self, request, *args, **kwargs):
-        db_objects = self.get_queryset()
-
-        if db_objects.count() == 0:
-            return Response(status=404)
-
-        db_object = db_objects[0]
-        version = int(self.kwargs.get("version", -1))
-
-        if version != -1 and db_object.version != version:
-            return Response(status=404)
+        db_object = self.get_object()
 
         # Check that the user can access it
         (has_access, open_source, accessibility) = db_object.accessibility_for(