after_show in DCATPlugin breaks custom theme

[metaodi]

I just traced a bug to the after_show method of the DCATPlugin.

I was not expecting, that the dcat plugin would do anything with my theme, but it ended up overriding the names of some attributes on the resources in my theme.

E.g. my theme relies on the existence of an attribute named res.rights, after activating the dcat plugin, this attribute is suddenly called res.Rights. (or res.download_url becomes res.Download URL)

I guess this is a convenience method to display the translated strings for all those that do not use a custom theme. But for those that do, this plugin might break it.

Is there a way to make this behavior optional or to put it in another plugin? What I now ended up doing is overriding the DCATPlugin, but I'm not sure if this is something everybody has to do, that is in a similar situation like me.

[amercader]

This could definitely be wrapped in a config option switch (ckanext.dcat.translate_keys) that allowed to turn this behaviour off. Happy to take a PR for it @metaodi