Provides the ability to specify how to finish processing a request when version validation fails.

Typically a handler will finish the request by responding with a 400 level HTTP status code. For example, Versionary.Plug.ErrorHandler responds to the request with a 406 status code and sets the body to Not Acceptable.

To create your own handler override the call/1 function of this behavior. A Plug.Conn will be provided as the only argument.

Keep in mind that Versionary.Plug.EnsureVersion will halt the request before calling a handler. Once a handler processes the error the plug request lifecycle will finish.

Example

defmodule MyAPI.MyErrorHandler do
  @behaviour Versionary.Plug.Handler

  def call(conn) do
    body = %{
      error: %{
        description: "Not Acceptable"
      }
    }

    conn
    |> send_resp(406, Poison.encode!(body))
  end
end

defmodule MyAPI.MyController do
  plug Versionary.Plug.VerifyHeader, versions: ["application/vnd.app.v1+json"]

  plug Versionary.Plug.EnsureVersion, handler: MyAPI.MyErrorHandler
end