Add a draft tag to unpublished items and minor improvements (#46)

* Add a draft tag to unpublished items

* Add X-Cache-Hit header

* Expose decoder interface in roster cards

* Manage decoder interface set to None

ram/roster/models.py

@@ -129,13 +129,21 @@ class RollingStock(BaseModel):
     def preview(self):
         return self.image.first().image_thumbnail(350)
 
+    # similar to get_decoder_interface_display in template render,
+    # but returns "-" if no decoder interface is set
+    def get_decoder_interface(self):
+        return str(
+            dict(settings.DECODER_INTERFACES).get(self.decoder_interface)
+            or "-"
+        )
+
     @property
     def country(self):
         return self.rolling_class.company.country
 
     @property
     def company(self):
-        return str(self.rolling_class.company)
+        return self.rolling_class.company
 
     def delete(self, *args, **kwargs):
         shutil.rmtree(