This method selects a voucher that is suitable for publication, adds a publish entry and returns the publication object with the voucher object.
A voucher is suitable for publication when it's active and hasn't been published yet.
Clearly define the source of the voucher
You must clearly define which source you want to publish voucher code from. It can be either a code from a campaign or a specific voucher identified by code.
In case you want to ensure the number of publishable codes increases automatically with the number of customers, you should use auto-update campaign.
Returns a publication object which embeds a published voucher.