Mailchimp: Double-Opt-In-Mail multilanguage

[markus-moser]

CustomerLanguage should be added via HTTP-Header in api calls.

see https://github.com/drewm/mailchimp-api/issues/148

[nicoadel]

Hey, is there already any way to make the opt in mail multilang?

[github-actions[bot]]

Thanks a lot for reporting the issue. We did not consider the issue as "Pimcore:Priority", "Pimcore:ToDo" or "Pimcore:Backlog", so we're not going to work on that anytime soon. Please create a pull request to fix the issue if this is a bug report. We'll then review it as quickly as possible. If you're interested in contributing a feature, please contact us first here before creating a pull request. We'll then decide whether we'd accept it or not. Thanks for your understanding.