Replace custom csrf with ring-anti-forgery

[mynomoto]

• It's a breaking change. It won't work without wrap-anti-forgery
• A custom error-handler is necessary as the default response from ring-anti-forgery don't send a X-CSRF-Token header. Example:

(defn custom-error-handler [request]
  {:status 403
   :headers {"Content-Type" "text/html"
             "X-CSRF-Token" *anti-forgery-token*}
   :body "<h1>Missing anti-forgery token</h1>"})

(wrap-anti-forgery {:error-handler custom-error-handler})

• Some modifications were necessary because the default response is not from castra. So no error handling on the client. I used the response status.

[micha]

This issue has been handled by changing the CSRF header name in a29d278fff207a8860e51e1f90b6329abf75fcca.