Allow to easily extend the TaxonsController

[coorasse]

Scenario
solidus_multi_domain wants to extend the TaxonsController. Since there is no way to override only the loading of the Taxon, it ends up overriding the entire show method.

Problem
solidus_frontend changes the show method to preload images: https://github.com/solidusio/solidus/blob/master/frontend/app/controllers/spree/taxons_controller.rb#L13

solidus_multi_domain does not receive the changes and we end up with a N+1 query when using both.

Solution
Extract the load_taxon method so that solidus_multi_domain can override only that specific method.

[kennyadsl]

Thanks, I like the change. I'm just a little bit afraid that if users have overwrote this action they could end up having an extra query. Maybe a line into the Changelog would be enough.

[kennyadsl]

This line was useless, right?

[coorasse]

yes. exactly. I also double checked to be sure but the find_by! raises an exception if the element is not found, returning 404.

[coorasse]

Good catch. Yes, that would happen.
Do you want me to add a note to the Changelog? Another option would be to call @taxon = load_taxon directly inside the action...even though I would prefer the current version.

[kennyadsl]

@coorasse let's go with just adding a line to the Changelog, thanks!

[coorasse]

Good. I updated the CHANGELOG and squashed. 👍

[kennyadsl]

Thanks!