global

def self.coerce(input)

own middleware or `rescue_from` handlers.
public contract that users can still `throw :error, hash` from their
Normalize heterogeneous inputs into an ErrorResponse. Preserves the 
def self.coerce(input)
  case input
  when ErrorResponse
    input
  when Grape::Exceptions::Base
    from_exception(input)
  when Hash
    new(**input.slice(:status, :message, :headers, :backtrace, :original_exception))
  else
    new
  end
end