def generate(value, expires_at: nil, expires_in: nil, purpose: nil)
      data = encode(Messages::Metadata.wrap(@serializer.dump(value), expires_at: expires_at, expires_in: expires_in, purpose: purpose))
      "#{data}--#{generate_digest(data)}"
    end
def generate(value, expires_at: nil, expires_in: nil, purpose: nil)
      data = encode(Messages::Metadata.wrap(@serializer.dump(value), expires_at: expires_at, expires_in: expires_in, purpose: purpose))
      "#{data}--#{generate_digest(data)}"
    end
Generates a signed message for the provided value.

 The message is signed with the +MessageVerifier+'s secret. Without knowing
 the secret, the original value cannot be extracted from the message.

   verifier = ActiveSupport::MessageVerifier.new 's3Krit'
   verifier.generate 'a private message' # => "BAhJIhRwcml2YXRlLW1lc3NhZ2UGOgZFVA==--e2d724331ebdee96a10fb99b089508d1c72bd772"