Header params overwritten when signing

[economou]

Hello,

I've been using this gem in combination with your OpenIDConnect gem. When converting an IdToken to JWT, I've been setting some header parameters like so:

claims = { ... }
id_token = OpenIDConnect::ResponseObject::IdToken.new(claims)
signing_key = '...'

jwt = id_token.to_jwt(signing_key) do |token|
  token.x5u = 'http://www.example.com/'
end

However, when upgrading the JSON::JWT gem from version 1.5 to 1.6, I have unit tests failing due to these header parameters being lost.

This is apparently caused by this change: calling dup here doesn't copy over the header data to the new object.