Specify an URL to redirect after logout via settings

[kidhab]

This change make it possbile to specify an URL via logout_redirect_url at config/app_config.yml. After logging out the application redirects to this URL.

We use is to redirect the logout of the Demo instance to the info page.

Maybe this is also useful for other foodcoops.

[yksflip]

Great, thank you! Maybe it would be good to have it in the app_config.yml.SAMPLE too?

[kidhab]

Great, thank you! Maybe it would be good to have it in the app_config.yml.SAMPLE too?

done.

[wvengen]

It sounds like it could be useful to be able to configure in the configuration screen - I think most settings are, just not those that are security sensitive (like, which parts can be overridden from the database). This helps self-service e.g. at foodcoops.net.

And I'd like to note this for the record, so that when others add new config options (that would be useful for foodcoops to set without help of an admin), they would consider adding the UI part as well.

Anyway, great idea, feel free but not pressed to implement it. Already an improvement!