In xml responses, if the result is an empty array we want the response
to look like this:
<posts type="array"/>
not like this (the default):
<nil-classes type="array"/>
This refactors controllers so that this is done automatically instead of
having to manually call `@things.to_xml(root: "things")` everywhere. We
do this by overriding the behavior of `respond_with` in `ApplicationResponder`
to set the `root` option by default in xml responses.
Refactor to use `render_error_page` to handle User::PrivilegeError
exceptions. This way these exceptions are logged to New Relic.
Changes:
* Anonymous users aren't automatically redirected to the login page.
Instead they're taken to the access denied page, which links to the
login/signup pages.
* JSON/XML error responses return `message` instead of `reason`.
Fixes POST/PUT API requests failing with InvalidAuthenticityToken errors
due to missing CSRF tokens.
CSRF protection is only necessary for cookie-based authentication. For
non-cookie-based authentication we can safely disable it. That is, if
the user is already passing their login + api_key, then we don't need
to additionally verify the request with a CSRF token.
ref: 2e407fa476 (comments)
